Oil viscosity- tune it or don't mess with it?

[nedfunnell]

My 1990 Camry calls for 10W-30 oil. I got oil for a change today, and it got me thinking again about messing with my oil viscosity. My manual calls for 10W30 in temperatures over 40°F- so it'll be 10 weight oil at room temperature, and no runnier than 30 weight oil at operating temperature.

So, I'm wondering if oil viscosity is something that I can tune/select/adjust as I see fit, or will something go awfully wrong if I use 5W30 instead? At operating temps, the viscosity should be the same, since they're both -W30, right? So the only difference is the cold start performance, so during a cold start, my oil will be 5 weight instead of 10 weight. Isn't that better? Any reason why I shouldn't?

Now, what if I want to mess with the hot viscosity? This is more serious since it's the viscosity the engine will have to deal with the whole time it's hot. If I put a -W20 oil in there, the oil would be runnier, and I've heard tell that that will result in a marginal increase in power and efficiency- but at risk of running the engine with a different oil viscosity than the wise engineer who designed the engine called for.

Thoughts?

 

[vshah]

i wouldn't mess with it personally, i trust the engineers who built my engine to recommend the right oil. if you're racing or something then I could see trying out different weights, but other than that I don't think it is worth the time and money.

 

[Zenmervolt]

The wider the viscosity range, the lower the compliance with the specification at either extreme. For example, my '98 S70 calls for 10w30 for ambient temperature ranges between -4 degrees and 104 degrees Fahrenheit. 5w30, while better for cold starts (down to below -22 degrees Fahrenheit) is only acceptable up to 86 degrees Fahrenheit. Similarly, while 5w40 is good from below -22 degrees to 104 degrees Fahrenheit, the manual cautions never to use 15w40 in any normal use conditions.

Basically, you'll want to check what the manufacturer recommends for your engine. When you start increasing the viscosity spread between the low and high numbers you decrease the compliance with the specifications for both numbers. Notice how in my example, both the 10w30 and the 5w40 have the same maximum ambient temperature (104 degrees Fahrenheit) even though the latter should be "thicker" when hot and better able to stand up to the heat.

ZV

 

[justfrank]

You really can't go wrong with 5w30 in anything, anywhere these days for older engines. 10w30 isn't ideal in cold winter weather as a comparison.

 

[Zenmervolt]

You really can't go wrong with 5w30 in anything, anywhere these days for older engines. 10w30 isn't ideal in cold winter weather as a comparison.

See the post immediately above you for why this is bad advice.

In every vehicle I own, 5w30 would be an absolute disaster during summer months.

Use what the manual says, full stop.

ZV

 

[Throckmorton]

As I understand, it takes more additives to make a 5W30 oil than a 10W30, so you're reducing the effectiveness of the oil at lubricating in order to get the cold start benefits.

A lot of cars have a light weight oil specified because that's how they get their EPA fuel economy numbers. Meanwhile in other countries a thicker oil is specified because it's what lubricates the engine best. Automakers and the government don't care if your car lasts to 200k miles. You should have scrapped your car at 75k and bought a hybrid anyway.

 

[Raizinman]

I live or travel to climates that are more extreme. I realize that the auto manufacturer give us their RECOMMENDATION for oil viscosity for overall and EPA figures. Because of that, I feel that I can tweak my oil selection a bit better. When I’m traveling to a VERY hot place in the summer, 5w20 is too thin for my liking and I’ll move to a 10w30. Likewise, in a different vehicle when traveling north in the winter, the standard 10w30 is too thick for my liking and I’ll drop to a 5w20 or so. Since I normally get oil changes twice a year, I will judge the driving I will be doing along with the anticipated climate and choose my oil accordingly. If I lived in San Francisco where the weather is always 72 degrees, I would thus follow the manufacturer’s recommendation.

 

[justfrank]

See the post immediately above you for why this is bad advice.

In every vehicle I own, 5w30 would be an absolute disaster during summer months.

Every dealer I've ever worked (34 yrs now) for uses 5w30 year round in older engines (new is now 5w20 or 0w20), including my 22 yrs with Volvo. I use synthetic 5w30 in all 3 of my cars year round, including my 2 older Volvo's.

As for temperature:

http://www.autosourcemotors.net/blog/car-maintence-tips/201--oil-viscosity-made-simple-5w30-vs-10w30

 

[Pulsar]

You really can't go wrong with 5w30 in anything, anywhere these days for older engines. 10w30 isn't ideal in cold winter weather as a comparison.

You can go very, very wrong. Please don't give advice if you really don't know what you're talking about. People who listen to you could make a very expensive mistake.

Follow the manufacturer's recommendation. Dealers frankly don't know crap about engine design, and routinely tell customers the WRONG thing to do.

A perfect example is that recently some dealers were filling the oil up to the top of the dipstick hashmark. They didn't pay any attention to the user manual that clearly showed them filling it up to the midpoint. As a result, they were telling their customers that the vehicles were not coming from the factory correctly, AND they were overfilling the engine causing the crank to go through way too much oil. Bad.

<------ Designs and builds 4.6, 5.0, and 6.2L for a major manufacturer.

 

[justfrank]

You can go very, very wrong. Please don't give advice if you really don't know what you're talking about. People who listen to you could make a very expensive mistake.

Follow the manufacturer's recommendation. Dealers frankly don't know crap about engine design, and routinely tell customers the WRONG thing to do.

It's NOT the dealers, it's the manufacturers that mandate what oil is used in their engines. Both Volvo and Toyota/Lexus have been using 5w30 for decades now and w/o ANY problems. The manufacturers have to warranty their engines and powertrain warranty is a long time these days SO, I think THEY know what their doing.

It's not me, it's not the dealers who've made these decisions. Do some research. I don't need to.

Follow the manufacturer's recommendation. Dealers frankly don't know crap about engine design, and routinely tell customers the WRONG thing to do.

A perfect example is that recently some dealers were filling the oil up to the top of the dipstick hashmark. They didn't pay any attention to the user manual that clearly showed them filling it up to the midpoint. As a result, they were telling their customers that the vehicles were not coming from the factory correctly, AND they were overfilling the engine causing the crank to go through way too much oil. Bad.

Never heard of that in my years of experience. We put in what the book requires and after the engine sits for a few minutes, the dipstick reads full. If it reads low, the customer who checks his oil level is likely to say something about that. I've never heard, read where any engine shouldn't have its oil level to the top of the dipstick after it sits.

 

[DVad3r]

I wouldn't mess with it. Sure you can use 5w30 in the winter and 10w30 in the summer, but I wouldn't use any higher viscosity.

My car calls for 5w30 year round.

My dad has a similar car to you, a 1992 Toyota Camry wagon with the I4 engine. He only uses 10w30 and has 550,000 km + on it and still going.

 

[LTC8K6]

Ford issued a tsb a while back that switched a bunch of older engines to 5W-20.

My 1995 Taurus 3.8L was included.

 

[Zenmervolt]

Every dealer I've ever worked (34 yrs now) for uses 5w30 year round in older engines (new is now 5w20 or 0w20), including my 22 yrs with Volvo. I use synthetic 5w30 in all 3 of my cars year round, including my 2 older Volvo's.

As for temperature:

http://www.autosourcemotors.net/blog/car-maintence-tips/201--oil-viscosity-made-simple-5w30-vs-10w30

Yes, because I'm going to trust a generic website over the engine-specific viscosity chart created by the people who actually designed the engine in my car.

Volvo does not recommend 5w30 for my car at any ambient temperature above 86 degrees Fahrenheit. While I'm sure that there's enough wiggle-room in the spec that running 5w30 in 90-degree temps would not cause the engine to grenade, it's still not a good idea.

I'll stick with what the owner's manual says for my car, thank you:

The reason that dealers use 5w30 in everything has NOTHING to do with it being the right oil to use and EVERYTHING to do with saving themselves money. For a dealer, 5w30 is "good enough" and any problems it causes aren't likely to be anything beyond increased oil consumption for most modern (~10 to 15 years old) cars in most climates (in the South during the summer things might be more problematic). Using the same oil in everything lets the dealer buy one big drum of oil instead of having to keep several different viscosities around. It's MUCH cheaper for them to use a "good enough" oil in everything than to use the right oil. It's still better to use what the manual recommends. In any case, in my experience dealership mechanics are generally at the same level as the guys at Jiffy Lube. If you want a real mechanic, you don't go to the dealer.

As for using it in everything, I'm sure as all hell not going to use 5w30 in my Porsche that calls for 20w50. People have tried that and end up with a nice healthy 5 PSI of oil pressure at hot idle. In freshly-rebuilt engines. On 70-degree days. We will charitably call that "less than ideal." Running the proper 20w50 gives between 30 PSI and 45 PSI of oil pressure at hot idle.

You just don't go blindly dicking around with what the engineers recommend.

ZV

 

[disappoint]

The wider the viscosity range, the lower the compliance with the specification at either extreme. For example, my '98 S70 calls for 10w30 for ambient temperature ranges between -4 degrees and 104 degrees Fahrenheit. 5w30, while better for cold starts (down to below -22 degrees Fahrenheit) is only acceptable up to 86 degrees Fahrenheit. Similarly, while 5w40 is good from below -22 degrees to 104 degrees Fahrenheit, the manual cautions never to use 15w40 in any normal use conditions.
ZV

Only acceptable up to 86F? That's funny because your engine runs at ~180F to 230F depending on the thermostat. I know you mean ambient air temp., but what's going to happen to 5W30 oil at 86F that makes it unacceptable?

 

[Ferzerp]

i wouldn't mess with it personally, i trust the engineers who built my engine to recommend the right oil. if you're racing or something then I could see trying out different weights, but other than that I don't think it is worth the time and money.

Well, the engineers don't always decide... Sometimes other factors come in to play.

With my car, there was an agreement between Dodge and Mobil 1. A certain weight was suggested. That agreement ended, and Pennzoil was the new partner. Pennzoil did not manufacture that weight. Magically, the closest weight Pennzoil has was the suggested weight for new cars!

I think they're reversed it now, but still, you see my point.

 

[Zenmervolt]

Only acceptable up to 86F? That's funny because your engine runs at ~180F to 230F depending on the thermostat. I know you mean ambient air temp., but what's going to happen to 5W30 oil at 86F that makes it unacceptable?

Even with the thermostat regulating coolant temperature, all engines are, to some degree, cooled by their oil as well and the oil needs to be able to dissipate the heat that it absorbs. It's also important to note that, regardless of coolant temps, combustion chamber temperatures are a couple thousand degrees, so there's a lot of heat energy being dissipated by an engine. As ambient temperatures increase, so to do sump temperatures, especially when idling. As the oil thins more from the higher temperatures, the ability to maintain adequate oil pressure when the engine is at idle decreases. On very warm days, the thermostat can cease to have any regulatory effect on coolant temps because it will eventually hit a point where it is full open all the time and the only regulation of temperature is the amount of air flowing over the radiator.

And, as I've already mentioned, a 5w30 oil is not going to meet the 30-weight requirements as well as a 10w30. Every viscosity rating has a range of values and anything falling within that range "counts" as having that rating. A 5w30 oil, all else being equal, will be a "thinner" 30 weight than a 10w30 as temperatures climb.

Nothing magically happens right at 86 degrees Fahrenheit, but there has to be a line drawn somewhere and the engineers clearly felt that 5w30 was not good up to 104 degrees Fahrenheit, so the line was drawn at the lower temperature interval.

ZV

 

[HybridSquirrel]

I use Rotella t6, its 5w40 and does the job. Dirt cheap too.

 

[desy]

too much drama over oil
I've read about lots of cars that have NEVER had their oil changed lasted 100's of thousand miles. 5-30 10-30 in a appliance car? Its no Porshe, never be a problem , Ford and Honda went to 5-20W to add a half mpg in their overall fleet vehicles to meet CAFE.

 

[Zenmervolt]

too much drama over oil
I've read about lots of cars that have NEVER had their oil changed lasted 100's of thousand miles.

I strongly doubt this. Even a car in fantastic condition is going to burn some amount of oil and there's no way that a car is going to go "100's of thousand miles" with the oil never being changed because at some point well before 100,000 miles it's going to run dry.

ZV

 

[MrPickins]

Every dealer I've ever worked (34 yrs now) for uses 5w30 year round in older engines (new is now 5w20 or 0w20), including my 22 yrs with Volvo. I use synthetic 5w30 in all 3 of my cars year round, including my 2 older Volvo's.

As for temperature:

http://www.autosourcemotors.net/blog/car-maintence-tips/201--oil-viscosity-made-simple-5w30-vs-10w30

You should read your own link:

When making a choice about which viscosity oil is the best for your engine, always consult your owner's manual if in doubt. Even a small difference, such as between 5W30 and 10W30, can save your engine from unnecessary wear.

 

[desy]

I didn't say they didn't add oil, but that it was never changed

http://www.physicsforums.com/archive/index.php/t-583602.html

"In the commercial and industrial worlds, we have become very much aware that the OEM will always suggest maintenance intervals that are extremely conservative. I know of one aircraft component, for example, where the recommended service interval was 50 hours. But after a great deal of research and testing, the FAA bought into a 5000 hour frequency. Then with additional effort to continually monitor the actual condition of the component in flight, the frequency got pushed out to 50,000 hours, or whenever the monitoring instrumentation detected a potential problem.

That is how the development of &#8220;Predictive Maintenance Engineering&#8221; has developed.

Then the other day I was in the shop where I bring my car, when I saw an engine being torn down. It was in absolutely the worst condition I had ever seen. When they pulled the valve cover off, I saw a mass of carbon that looked like a valve cover. This was from a Toyota pickup truck owned by an auto parts store. They used it as a delivery truck, the worst possible service. They had never changed the oil, ever. Yet they drove it into the shop with a new motor in the bed and a little more than 400,000 miles on the odometer. The engine had finally lost enough compression that the owner decided it was time to do something with it.

So everything people tell me about how not changing the oil makes the old oil break down and do bad things is true. But it seems that the commonly assumed change intervals are extremely conservative. How much longer do you think this engine would have lasted beyond 400K before they would have had to replace it anyway, if they had changed the oil every 3K? How many of us would have kept the truck long enough for it to accumulate that many miles?"

Here is an actual director of Castrol motor oil

http://www.dutchdailynews.com/oil-change/

 

[Zenmervolt]

I didn't say they didn't add oil, but that it was never changed

http://www.physicsforums.com/archive/index.php/t-583602.html

"In the commercial and industrial worlds, we have become very much aware that the OEM will always suggest maintenance intervals that are extremely conservative. I know of one aircraft component, for example, where the recommended service interval was 50 hours. But after a great deal of research and testing, the FAA bought into a 5000 hour frequency. Then with additional effort to continually monitor the actual condition of the component in flight, the frequency got pushed out to 50,000 hours, or whenever the monitoring instrumentation detected a potential problem.

That is how the development of &#8220;Predictive Maintenance Engineering&#8221; has developed.

Then the other day I was in the shop where I bring my car, when I saw an engine being torn down. It was in absolutely the worst condition I had ever seen. When they pulled the valve cover off, I saw a mass of carbon that looked like a valve cover. This was from a Toyota pickup truck owned by an auto parts store. They used it as a delivery truck, the worst possible service. They had never changed the oil, ever. Yet they drove it into the shop with a new motor in the bed and a little more than 400,000 miles on the odometer. The engine had finally lost enough compression that the owner decided it was time to do something with it.

So everything people tell me about how not changing the oil makes the old oil break down and do bad things is true. But it seems that the commonly assumed change intervals are extremely conservative. How much longer do you think this engine would have lasted beyond 400K before they would have had to replace it anyway, if they had changed the oil every 3K? How many of us would have kept the truck long enough for it to accumulate that many miles?"

Here is an actual director of Castrol motor oil

http://www.dutchdailynews.com/oil-change/

Because everyone wants to be driving around with an engine that's 50% down on power and barely running.

I'm not arguing for a 3,000 mile oil change interval here. It's perfectly fine to go until you get actual degradation showing on a used oil analysis, which can absolutely be many times longer in some cases.

What you're failing to take into account, however, is that engines are remarkable resilient things. Most engines will still "run" even if there are massive vacuum leaks and huge amounts of blow-by. Most people aren't going to be willing to put up with the crap that happens if you never change your oil.

A local delivery truck just isn't treated the same as a personal vehicle. If the truck breaks down, it just means you get paid to sit there while someone else from work comes out to get you. With my personal vehicles, I want to be (and am) confident that I could go out, hop into (or onto) any of them and drive from Seattle to Key West. If a work delivery truck blows a bunch of oil smoke out the tailpipe, you don't care.

In addition to all that, "never change the oil" is still very unlikely, even for the truck you cite. Firstly, you didn't talk with the actual owner; the guys at the shop don't know for certain whether the oil was literally never changed. Secondly, I know so many people who "never change their oil, ever" who actually change it every 10,000 miles or so, they just talk in hyperbole. On the balance of probabilities here it seems likely that you are simply taking the mechanic's hyperbole at face value.

I've seen this before. It's always the same. Someone's friend/brother-in-law/sister's friend's father's cousin/mother's bridge partner's doctor's brother owned X brand/model of car that got 150 mpg/went 200 mph/lasted 150 years and it always "just goes to show that you really don't need to follow all the directions they give you in the owners manual." These sort of "so-and-so's car lasted forever and we never changed any fluids at all" are just like the stories about 150mpg carburetors; car guy versions of old wives' tales.

Also, do you even know what a director of a company does? They're guys in suits who don't need to (and essentially never do) know anything whatsoever about day-to-day operations of a company, much less anything about the chemistry behind when oil needs to be changed. The former director of Castrol likely has far less understanding of the intricacies of lubrication than the posters on Bob Is The Oil Guy's forums.

ZV

 

[Raizinman]

The owner&#8217;s manual for oil is a RECOMMENDATION. Other things in the manual will say: You must use or must do. Oil is not listed like this because you CAN tweak your oil usage. The temperature charts for oil are there so that you can choose your temperature zone and pick the oil that best suites you. On my 2012 Honda, the manual recommends 0w20 for all the time. Again, this is Honda&#8217;s recommendation. The manual does not state that you must use 0w20. When traveling to a very hot climate, I will change to thicker oil, most likely a 10w30. Don&#8217;t get confused by recommendations.

 

[LTC8K6]

The owner&#8217;s manual for oil is a RECOMMENDATION. Other things in the manual will say: You must use or must do. Oil is not listed like this because you CAN tweak your oil usage. The temperature charts for oil are there so that you can choose your temperature zone and pick the oil that best suites you. On my 2012 Honda, the manual recommends 0w20 for all the time. Again, this is Honda&#8217;s recommendation. The manual does not state that you must use 0w20. When traveling to a very hot climate, I will change to thicker oil, most likely a 10w30. Don&#8217;t get confused by recommendations.

My owners manual states very clearly that I must use 5W-20. It's not a recommendation.

2008 Jeep.

 

[LTC8K6]

2012 Mustang oil spec, not recommendation.

To protect your engine and engine&#8217;s warranty, use Motorcraft SAE
5W-20 or an equivalent SAE 5W-20 oil meeting Ford specification
WSS-M2C945-A. SAE 5W-20 oil provides optimum fuel economy and
durability performance meeting all requirements for your
vehicle&#8217;s engine. Refer to Maintenance product specifications and
capacities later in this chapter for more information.
Do not use supplemental engine oil additives, cleaners or other engine
treatments. They are unnecessary and could lead to engine damage that
is not covered by Ford warranty.