5W30 diesel rated oil

[RalphVa]

I've experienced about 2 mpg increase on the 1983 240D (31 vs. 29) and 1 mpg increase on the 2005 Tacoma 2.7 L (26.5 vs. 25.5). That's a pretty solid 4-6% increase in fuel mileage. The difference is probably mostly due to less oil pumpage hp loss, particularly until the engine heats us. I really noticed the difference on the Tacoma when I switched to 0w20 instead of 0w30 as well. The 1.0 mpg increase is a combo of the 0w20 and 0w30.

Toyota has a notice on the oil fill cap: "5w30 only". I figure the 0w20 has probably about the same vis at higher temperatures (than the 210 F that the "20" of "30" is rated for) because of the much flatter vis-temperature line for the synthetic. Of course, at starting temp, the vis will be MUCH lower but still higher than at operating temperature.

If you haven't dealt with computing viscosity at other temps, you may not understand much of this. I used to do it all the time.

Ralph

 

[DarkBlack]

You don't really think the slight oil-pump load change equates to a 4-6% total vehicle MPG load do you??

 

[Tractor Seabee]

My Vote is: The best all around oil for everything is DELO 400D, comes in several weights. I have used it for 50 years from stationary diesels to small gas engines. Originally designed by Standard Oil for hard service diesels.

ron

 

[RalphVa]

All I know is what I've measured. Probably a combo or better pump efficiency plus lower engine friction, particularly in the lifter areas.

Racers use synthetics because they give more power. Why? Less friction is likely.

Ralph