Just wondering about oil selection. I have been using Mobil1 10W30 but I looked at the owners manual and it says to use 5W30. What is the difference? What do you guys use? And yes, I have checked the FAQ's.

 

You can use either one. Although there is a technical service bulliten for our car and it says to use ONLY 5w30. This may have to do with the VTC. But you should be safe with both.

 

i use 10w30 and i havent had any problems out of my performance

 

other suggestions/comments?

 

Kinda depends on the type of driving that you do and the area that you live.

I mostly use Mobil 1 15w50 because I do mainly highway and/or high rpm driving. The type of driving where the car can warm up, the oil can reach operating temperature, then stay there for a while. I also live in a warm area (SF Bay Area). I also run the 15w50 because there are no friction modifiers (the oils that have them indicate Energy Conserving on the API seal). Friction modifiers in the oil improve fuel economy by like 1.5 percent or something but tend to not protect engine parts as well.

If I know that I'll be going to Tahoe to ski where there's snow and/or I do a lot of little 5 minute trips, I'd switch to 5w30 or 10w30, so that the oil can circulate more easily to the top of the engine when the car is cold. The thinner oils are easier for the oil pump to pump to the top of the engine when cold.

I use 15w50 in my 4th Gen, Miata, and motorcycle, but use 10w30 in my 3rd Gen and truck because of the type of driving.

-V

 

The real key in an oil's ability to protect your engine is the film strength. In the old days of dino oil only, a thicker viscosity often gave better strength, however, the film strength of a synthetic 10-30 (or 5-30) is far superior to a dino 10-40 or 20-50.

I use Royal Purple because its film strength is significantly higher than even Mobil-1, plus it has molecular bonding, leaving a microscopic sticky thin film on metal parts, which reduces wear during startup, before the oil pressure has built. Having this protection, using the thinnest vicosity reduces horspower wasted pumpning unnecessarily thick oil, plus it will reach VTCs and other small areas with much greater ease, especially when cold. I use 5-30, summer and winter.

John

 

What about older engines? I have a '91 VG 5spd with 132000 miles. The heads were rebuilt at 119,000 though.

 

Older engines are a different story in that if minor play has developed because of wear, thicker viscosity oil tends to quiet it down. That's why you can run 20-50 in many American engines and quiet them down. They are big, and often have looser tolerances.

On a tight machines like Japanese engines (prior to advanced wear) it's a different story. US engine oil flow, as a rule, is high volume low(er) pressure. Japanese engine is low(er) flow, higher pressure, hence the benefit of using low viscosity oil.

Look at any precision high speed tool (like dental tools) the oil used is water thin.

John

 

If you have been using Mobil 1 and have no leakage problems you should be fine. The difference is the weight laymans term "thickness" of the oil at temp. 5W-30 will yield better gas mileage than 10W-30. 5W-30 is thinner at cold startup but at operating temp it is the same.

 

5W-30
5 - weight of oil when cold
W - all weather (or something to that effect)
30 - weight of oil when hot

10W-30 compared to 5W-30
oil is thicker when cold...same when hot.