YACT: Engine Oil Recommendations

[Quixfire]

I noticed there is a lot of confusion on this forum about the proper engine oil type or viscosity someone should use in their vehicle. I have put together a short statement to clarify the issue for the many of you who do not have the experience in professional engine repair or design to help understand why it is important to use the correct type of oil in your engine.

There are two main reasons why vehicle manufacturers recommend thinner or lighter viscosity grades of motor oil. First, a gain in fuel economy can be achieved with lower viscosity oil. At cold temperatures and at start up, lower viscosity oil will reduce internal engine friction. About 10% of the engine's horsepower is lost to internal engine friction, resulting in a drop in fuel economy. Additionally, vehicle manufacturers are struggling to meet Corporate Average Fuel Economy (CAFE) requirements set by the government and avoid paying associated fines. Any fuel mileage improvement associated with a lubricant use would be good for them, and lighter viscosity grade motor oil will make a difference.

Second, thinner motor oil is essential for easy starting, particularly in cold weather, and for proper lubrication once the engine starts. Today's smaller engines have smaller clearances and tighter tolerances between moving parts, and there have been some instances where camshaft damage has occurred because of inadequate lubrication with higher viscosity grades in colder weather. Thinner oils, such as SAE 5W-30, will flow faster than heavier motor oils during start-up and initial engine operation and will help protect the engine from excessive wear. Multigrade oil will also offer the same high temperature protection as single grade motor oil. Always check your vehicle owner's manual to select the proper viscosity grade based on the expected temperature range.

The viscosity grade(s) recommended by the vehicle manufacturer depend somewhat on engine design. Engine manufacturers have spent considerable time and expense experimenting with different viscosity grades and have indicated in the owner's manual the grades they feel will best protect the engine at specific temperatures. While one manufacturer's engine may require an SAE 10W-30, another manufacturer's engine may require an SAE 5W-20 viscosity grade. This is likely due to different tolerances within the engine or other engine design factors.

 

[XZeroII]

A hint that those fat cats who design vehicles don't want you to know is that you can use water in place of oil. Look at people who go water skiing, they are just gliding along. And what about fish? Feel how slippery they are? That's because of water. Put that stuff in your engine and it will work beautifully.

 

[mugs]

That's interesting, but every other article I've read on the Internet (including on AMSOIL's site, and they make a synthetic 5W-20) says it's alright to use 5W-30 if your engine requires 5W-20.

Edit: I know you can't believe everything you read on the Internet, but one good reason to believe this is that the exact same engine that used to require 5W-30 now requires 5W-20.

 

[rayray2]

Well I live in Texas and I really don't think it matters if I put in 30W, 10W30, or 5W20. It's all good..

 

[TechnoKid]

Remember that a 10w30 will shear down less than a 5w30 would, this is because of the viscosity index improvers that the oil makers must add to the 5w30 to get that viscosity spread. If you can use a 10w30, then by all means use it. A 5w30 and a 10w30 are the same "weight" its just that the first figure designates the cold flowing/pumping characteristics of the oil. A 5w30 and a 10w30 should have the same viscosity at 100C (relative within the specs of being considered a 30 weight oil).

BITOG Is a good site to read up on oil. There forums are full of used oil analysis and info on oil and filters.

Good post, btw, quixfire.

I will add more later, I have to get to class.

 

[flyfish]

The vast majority of oil related problems are not from using the wrong type of oil, but simply not changing the oil in a consistent, timely fashion.
Also, people do not check their oil level between changes and the oil level becomes very low by the end of their oil change interval. This is very bad.
For most vehicles 4500-6000 miles is a very safe OCI, IF you keep the correct oil level!! The type of oil used is less of an issue.

 

[Electric Amish]

What if I don't have an owner's manual??

 

[Scootin159]

Originally posted by: XZeroII
A hint that those fat cats who design vehicles don't want you to know is that you can use water in place of oil. Look at people who go water skiing, they are just gliding along. And what about fish? Feel how slippery they are? That's because of water. Put that stuff in your engine and it will work beautifully.

Unfortunatly with the temps a engine runs at you no longer have water (the only reason you still have water in the radiator is because it's a presurized system). Also engines require a bit more lubrication than water can provide (although you are absolutly right that water can act as a lubricant.....try hitting the brakes hard in the rain to learn that one).

 

[Scootin159]

Originally posted by: Electric Amish
What if I don't have an owner's manual??

You can normally get one cheep enough if you look in the right place. Otherwise just run 10w30 as it'll work adequately for most cars (maybe not ideal, but it's a 'safe' guess).

 

[Vette73]

I would NOT use 5W20 and have told all my customers with Hondas and Fords that as well. It is a gimmick done by them to get juts a hair better gas milage on their national averages which in turn saves THEM money by lowering fees/taxs set by the federal goverment.

What I tell all my customers is.....

10W30 for most climates, 5W30 if you live in a very cold climate, and 20W50 if it leaks and/or smokes real bad.

 

[Eli]

Originally posted by: rayray2
Well I live in Texas and I really don't think it matters if I put in 30W, 10W30, or 5W20. It's all good..

You couldn't be more wrong.

Especially living in Texas.

 

[Howard]

Originally posted by: Marlin1975
I would NOT use 5W20 and have told all my customers with Hondas and Fords that as well. It is a gimmick done by them to get juts a hair better gas milage on their national averages which in turn saves THEM money by lowering fees/taxs set by the federal goverment.

What I tell all my customers is.....

10W30 for most climates, 5W30 if you live in a very cold climate, and 20W50 if it leaks and/or smokes real bad.

Why not 5W20?

 

[Eli]

Originally posted by: Howard

Originally posted by: Marlin1975
I would NOT use 5W20 and have told all my customers with Hondas and Fords that as well. It is a gimmick done by them to get juts a hair better gas milage on their national averages which in turn saves THEM money by lowering fees/taxs set by the federal goverment.

What I tell all my customers is.....

10W30 for most climates, 5W30 if you live in a very cold climate, and 20W50 if it leaks and/or smokes real bad.

Why not 5W20?

Cuz most of us gearheads have the strange idea that 5W-20 is much like 3-in-1 oil.

lol...

In all honesty, it probably isn't going to make that much of a difference, unless you live in 110 degree heat.

It would probably be better to use 5W-20 in an engine designed to run 5W-30, than it would be to use 10W-40.

Of course, this all depends on your climate.

 

[TechnoKid]

Here is a good thread on BITOG that is somewhat of a cliffnotes about oil.

There is nothing wrong with 5w20 oil, imo. There have been some great UOAs (used oil analysis) on BITOG with cars that have used 5w20. A Xw30 would be able to protect the same if not better than a 5w20 because it's a bit thicker at operating temps (around 100C), which creates more "cushion" between moving parts. A typical 5w20 has a viscosity of 8.5-9.5 cSt at 100C, where as a Xw30 has a typical viscosity of 10-12 cSt at 100C. However, in theory, the 5w20 should be more shear stable than a 5w30 because it has less of a viscosity spread. All oils shear some as they wear, but the more shear stable the oil, than the longer it can offer the protection of that viscosity.

As far as the Xw portion rating of the oil, a typical 0W has a cSt of 40 @100C, where as a 5w has a cSt of 56 @ 40C. Mobil 1 Synthetic 5w30 pour point is -45C using ASTM D 97, but this should not be a gauge of its absolute cold pumping temperature. Sythetics will almost always pump better at colder temps then the same would in conventional dino. A 0w30 is not "thinner" than a 5w30; they have the same cSt at opertaing temp of 100C, it just flows better at colder temps. It is correct to say that a 5w20 is thinner than a 5w30.

CAFE (corporate average fuel economy), imo, may have alot more to do with what weight oil a manufacturer will spec, more so than engine design factors.