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10w30, 10w40, 20w50, 5w30 - what is the difference?

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SagaLore

SagaLore

Elite Member
What do all the different oil weights do, what is good for what? I'm assuming that 10w40 is heavier than 10w30. Right now I have 30 in my car, but the rings are wearing out and I'm losing performance and fuel efficiency - if I put 40 in, can I gain some of that back?
 
There should be a lot of links on this out there. Be careful with heavier oil, as it can affect engine wear at start-up and may be affected by the temperatures you're driving in.
 
The first number is its cold start viscosity. The higher the number, the thicker the oil. In really cold climates, 0w-something is good since it's easier to get oil flowing during cold starts. But for most climates 5w-something is just fine.

The second number is the oil's viscosity when it's heated up. For most cars, something-w30 is fine, since it provides adequate protection in most situations.

A good guideline to go by is what's on your car's oil cap says. Mine says 5w30, so that's what I use.
 
Originally posted by: jumpr
The first number is its cold start viscosity. The higher the number, the thicker the oil. In really cold climates, 0w-something is good since it's easier to get oil flowing during cold starts. But for most climates 5w-something is just fine.

The second number is the oil's viscosity when it's heated up. For most cars, something-w30 is fine, since it provides adequate protection in most situations.

A good guideline to go by is what's on your car's oil cap says. Mine says 5w30, so that's what I use.
Click to expand...

thanks! ive always wondered what those numbers were for, the oil change place puts 5w20 in my suv
 
Originally posted by: jumpr
The first number is its cold start viscosity. The higher the number, the thicker the oil. In really cold climates, 0w-something is good since it's easier to get oil flowing during cold starts. But for most climates 5w-something is just fine.

The second number is the oil's viscosity when it's heated up. For most cars, something-w30 is fine, since it provides adequate protection in most situations.

A good guideline to go by is what's on your car's oil cap says. Mine says 5w30, so that's what I use.
Click to expand...


thats what they say but it's kind of counterintuitive that oil gets thicker as it gets hotter.

 
Originally posted by: OS
Originally posted by: jumpr
The first number is its cold start viscosity. The higher the number, the thicker the oil. In really cold climates, 0w-something is good since it's easier to get oil flowing during cold starts. But for most climates 5w-something is just fine.

The second number is the oil's viscosity when it's heated up. For most cars, something-w30 is fine, since it provides adequate protection in most situations.

A good guideline to go by is what's on your car's oil cap says. Mine says 5w30, so that's what I use.
Click to expand...


thats what they say but it's kind of counterintuitive that oil gets thicker as it gets hotter.
Click to expand...

Right, the oil gets thinner. I think oil is actually a combination of two different oils, the 10W is the viscosity of the first oil at cold temp, and the 40 is the viscosity of the 2nd oil while it's hot.
 
Originally posted by: Ameesh
Originally posted by: jumpr
The first number is its cold start viscosity. The higher the number, the thicker the oil. In really cold climates, 0w-something is good since it's easier to get oil flowing during cold starts. But for most climates 5w-something is just fine.

The second number is the oil's viscosity when it's heated up. For most cars, something-w30 is fine, since it provides adequate protection in most situations.

A good guideline to go by is what's on your car's oil cap says. Mine says 5w30, so that's what I use.
Click to expand...

thanks! ive always wondered what those numbers were for, the oil change place puts 5w20 in my suv
Click to expand...

Do you own a late model Ford or Honda? I hate that they use 5W-20, it's hard to find synthetic 5W-20 around here.
 
Originally posted by: SagaLore
Originally posted by: OS
Originally posted by: jumpr
The first number is its cold start viscosity. The higher the number, the thicker the oil. In really cold climates, 0w-something is good since it's easier to get oil flowing during cold starts. But for most climates 5w-something is just fine.

The second number is the oil's viscosity when it's heated up. For most cars, something-w30 is fine, since it provides adequate protection in most situations.

A good guideline to go by is what's on your car's oil cap says. Mine says 5w30, so that's what I use.
Click to expand...


thats what they say but it's kind of counterintuitive that oil gets thicker as it gets hotter.
Click to expand...

Right, the oil gets thinner. I think oil is actually a combination of two different oils, the 10W is the viscosity of the first oil at cold temp, and the 40 is the viscosity of the 2nd oil while it's hot.
Click to expand...

It's actually just one kind of oil with polymers or something like that. It doesn't get "thicker" when it gets hot, it has the viscosity that the thicker oil (40 weight) WOULD have at that temperature, as opposed to the viscosity that a 10 weight oil would have at high temperatures.
 
Originally posted by: mugs
Originally posted by: Ameesh
Originally posted by: jumpr
The first number is its cold start viscosity. The higher the number, the thicker the oil. In really cold climates, 0w-something is good since it's easier to get oil flowing during cold starts. But for most climates 5w-something is just fine.

The second number is the oil's viscosity when it's heated up. For most cars, something-w30 is fine, since it provides adequate protection in most situations.

A good guideline to go by is what's on your car's oil cap says. Mine says 5w30, so that's what I use.
Click to expand...

thanks! ive always wondered what those numbers were for, the oil change place puts 5w20 in my suv
Click to expand...

Do you own a late model Ford or Honda? I hate that they use 5W-20, it's hard to find synthetic 5W-20 around here.
Click to expand...


Don't use 5W20 it is aq gimmick that Honda and ford came up with to save money on fees the goverment charges for gas milage per car.

Use Mobil1 5W30 or 10W30 year round and you will be ok
 
Oils of today are called "multi-viscosity". A 10w-30 oil has the flow characteristics of a 10 weight when cold (so lube can be rushed to where it needs to go) but a 30 weight when at operating tempeature.

Oil DOES NOT get thicker as it warms up. It gets thinner. The viscosity diferential is less from hot to cold with a 10w-30 then with a straight 30 weight. It still gets thinner.
 
It is rather odd, GM recommends to use 5w30 on my 01 Astro (4.3L V6), while my dad's old 95 bonneville used 10w30(3.8L v6)

I guess it depends also on how new the engine is, I thought it was based on engine size (cc) in the past, but i see now it has nothing to do with it anymore.
 
Vette73 said:
Don't use 5W20 it is aq gimmick that Honda and ford came up with to save money on fees the goverment charges for gas milage per car.


It’s actually not a gimmick. The oil they chose to use was a little thinner and was used to help with fuel consumption. The thicker the oil, the more power it takes to operate the engine. However there are some oils that do a better job of protecting your engine based on there weight.

I will say that in my opinion, Mobil 1 has always been the best. There synthetic oils are the best you can get.

One time I got in a rush changing my oil and accidentally got 5w-20 instead of 5w-30. My oil pressure gauge was all over the place. It was running slightly lower psi. at idle and the needle would move a lot depending on what rpm I was at.

On the next oil change I went back to my regular 5w-30 and everything went back to normal.
That being said, the thinner oils can cause this to happen. In today’s newer cars you should always use the manufacturers recommended weight. Works every time.
Click to expand...

Welcome to the Forums mercman. You have replied to a thread posted 14 years ago.
Please feel free to start a new thread rather than bumping an old one.

Iron Woode
Super Moderator
 
Last edited by a moderator:
If my calculations are correct I would have been near the end of my 2nd college semester when this thread was made. 😛

Hopefully OP got an oil chance since then.
 
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