holden j caufield
Diamond Member
seems like a lot of cars nowadays are at 5w20
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why use thicker oils if thinner improves MPG? 10w40 seems outdated now
- Thread starter holden j caufield
- Start date
Analog
Lifer
Well, since Eli the oil expert 😉 hasn't chimed in yet... The viscosity of your oil depends a lot on your climate, and engine specifications. Engines have tighter specs today than 30 years ago when 10W40 was the norm. I can say that without a doubt, as I worked as a coop student at Olds back when they built the rocket V8. They used to hand fit each piston! There was a guy on the line that had 4 different size pistons, and he fitted the right one based on the clearance in the cylinder! Today, with automation, piston size, as well as most other machined parts are much more precise and repeatable.
There has been many-a-debate on using thinner oils to get better gas milage at the expense of engine wear. I'm not sure about that. Then again, I'm pretty religeous about changing oil every 3,000 miles.
🙂
There has been many-a-debate on using thinner oils to get better gas milage at the expense of engine wear. I'm not sure about that. Then again, I'm pretty religeous about changing oil every 3,000 miles.
🙂
The Stigenator
Lifer
mine uses 5w30, but ford changed it to 5w20 for CARB reasons it gave them a bit more mileage over the board for all cars.. but i still use 5W30...
Thinner oils flow more easily, which means that lubrication will not be as high as when a higher viscosity oil is used. This may mean inadequate lubrication to high load parts - particularly main bearings.
When engine tolerances where less good, a thicker oil was essential to ensure that the did not simply drain through gaps and was retained on the moving surfaces. Modern engines have much tighter tolerances so can be well protected with a thinner oil - with the proviso that the lubrication system has to be designed to operate with that grade of oil.
Some modern cars are quite fussy about oil viscosity - e.g. the Ford focus requires 5W30 oil - no other grade is acceptable. A range of 5W30-10W40 was originally specified, but a design flaw on the valves meant that they stuck if 10W40 was used. Using a lighter oil (e.g. 0W30) won't do either - the lubrication pressure isn't high enough, and as a safety precaution the engine management will not start the engine because of the low oil pressure.
Climate is certainly important - and a thinner oil should be used in colder climates. With multigrade oils, it's optimal to adjust only the 'cold' viscosity (i.e. the 5 in 5W30) for climate. The 30 in 5W30 refers to the visocity when the engine is at normal operating temperature (which is the same regardless of climate). So if your engine specifies 10W40, then changing to 5W40 or 0W40 would probably be better for cold weather - because the oil retains the same characteristics once warmed up. However, such heavily viscocity modified oils like 0W40 only have limited availability, so aren't usually OEM specification.
When engine tolerances where less good, a thicker oil was essential to ensure that the did not simply drain through gaps and was retained on the moving surfaces. Modern engines have much tighter tolerances so can be well protected with a thinner oil - with the proviso that the lubrication system has to be designed to operate with that grade of oil.
Some modern cars are quite fussy about oil viscosity - e.g. the Ford focus requires 5W30 oil - no other grade is acceptable. A range of 5W30-10W40 was originally specified, but a design flaw on the valves meant that they stuck if 10W40 was used. Using a lighter oil (e.g. 0W30) won't do either - the lubrication pressure isn't high enough, and as a safety precaution the engine management will not start the engine because of the low oil pressure.
Climate is certainly important - and a thinner oil should be used in colder climates. With multigrade oils, it's optimal to adjust only the 'cold' viscosity (i.e. the 5 in 5W30) for climate. The 30 in 5W30 refers to the visocity when the engine is at normal operating temperature (which is the same regardless of climate). So if your engine specifies 10W40, then changing to 5W40 or 0W40 would probably be better for cold weather - because the oil retains the same characteristics once warmed up. However, such heavily viscocity modified oils like 0W40 only have limited availability, so aren't usually OEM specification.
It all depends on what the manufacturer of the engine has in mind and the environment the automobile will be in.
The 3SFE in my Dad's Camry specs anywhere from xW-30 to 20W-50.
We run Mobil Delvac 15W-40 in it.
Waiting until he racks up enough miles to do an oil analysis again. Will take about a year.
It is my hypothesis that the oil will need to be changed about every 6,000 miles, or every year. My dad doesen't drive very much.
It was ALMOST fine after 8 months and 4800 miles the last time we had it analyzed, but it also revealed a headgasket leak which was artificially degrading the oil.
This is a conventional oil, btw.
🙂
The 3SFE in my Dad's Camry specs anywhere from xW-30 to 20W-50.
We run Mobil Delvac 15W-40 in it.
Waiting until he racks up enough miles to do an oil analysis again. Will take about a year.
It is my hypothesis that the oil will need to be changed about every 6,000 miles, or every year. My dad doesen't drive very much.
It was ALMOST fine after 8 months and 4800 miles the last time we had it analyzed, but it also revealed a headgasket leak which was artificially degrading the oil.
This is a conventional oil, btw.
🙂
SeaSerpent
Platinum Member
Both of my 2004"s uses 5-30.
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