This was about the time the EPA and eco-warriors gained a foothold. My '83 warrentee manual said the use of 5w-30 above 50 deg F. was not recommended and would void the warrentee. By '91 or so it was recommended for all temps. The clearances weren't changed--just the specs for oil. The use of thinner oil gained the OEMs (including Toyota) a few years on the CAFE standards without having to make any mechanical changes. The manufacture's sold their soul to save money and not have to actually improve the engine by going to thin oil. Al Gore is is a fraud and if you want to jump off that cliff, go for it. Me; I'm going to use the the best oil to protect my engine. And it ain't 5w-30! Your mileage may vary! (but you engine longevity won't) Off my soap box so others may jump on...

Bugs

 

ehh... it all lubes. but if you want to get anal about oil, i prefer pennzoil 10w-30 syntetic. good all around oil and i hate to admit it but i bought into the 'synthetic' fad.

 

I just put 5W30 NAPA synthetic in mine. The 5-Speed tranny is getting synthetic next since it requires a pry bar to shift when cold at -20 like it was a few mornings ago...

 

Well when I did the oil change I used dino Castrol 5w-30. I am doing a rinse phase of Auto RX and need to use dino oil, so I wasn't able to use synthetic.

I figured I'd use 5w-30 for the winter, but now I'm not sure it was a good idea. I know the 5w will be beter for cold winter starts, but I have also read that a 5w-30 may not be actually a 30 weight oil at temperature, and a 10w-30 will be closer to 30 weight at temperature, do to the viscosity extenders that make a 5w-30 a supposed 30 weight at temperature. Is that true? I don't want to be running a 5w-30 if it's not gonna be at least 30 weight an operating temp. Bobistheoilguy will make your head spin if you read it too long, and you can never get a real answer.

I don't have an oil pressure gauge on my dash, no SR5 gauges yet, so not sure about pressure at opertaing temp. I might start thinking about using a 10 or 15w-40 in the summer too.

The chart posted above, from the '89 FSM, doesn't make any sense to me. According to it, at 50 degrees F, you can use either a 5w-30, 10w-40 or 25w-40?? Doesn't clear much up.

 

https://www.yotatech.com/forums/f116...l#post51280105

At 50 deg F, the 5, 10 & 20 weight will all flow fine at startup. At operating temp, they are all 30 or 40 weight, which is the recommended viscosity for an engine at operating temp: the 30 or 40 for a new, tight engine, the 40 or even a 50 when it has some miles behind it and the bearing tolerances have loosened up. So any of them would theoretically work fine above 50 deg, although in a practical sense, after a few thousand miles of use, the 5w30 viscosity may drop below 30 weight, and would probably not provide as much protection as the other two.

The main difference between those oils is for how low a temp they would be okay to use. The 20w I wouldn't use below 30 deg F; the 10 I would use only above 10 deg F or so, and below that I'd use the 5w. If it were really cold, a 0w-30 would be best.

 

MMCPECK: In addition to what the post above me states, the 5W30 is where I believe the synthetic VS. dino debate really leans toward synthetics. Synthetics don't use the viscosity extenders that dino oil uses to achieve that range so the viscosity breakdown issue is really not a factor.

 

15w40 with Lucas in both my trucks, all year round. Haven't had the Toyota long enough to comment but never an issue with the Nissan

 

Google this, "Ferraricha / Dr. Ali E. Haas AEHASS". Looks like a good read to me, oil info that is.

 

Ferrarichat*

 

Teuf, that Ferrarichat post from Dr. Hass is one of the most informative things I have ever read on motor oil....long, but good read. Thanks for sharing that.

 

Was so good I went to 5/30 syn blend last oil change, after 22 years of dino.