Thickest oil grade you have run in winter, summer?

[Shannow]

25W-70 in winter in my J-Car...SAE 30
0W-16 with a 20W60 high bright stock "additive" in summer.

 

[Bullwinkle007]

Vr50 valvoline racing oil in old 89 cavalier and 86 ranger v6 year round back in the 90s.
0w20 m1 in 2000 civic si ... revving to 8200 a lot in the summer.

Wouldn’t run any 0/20 ever. It’s for cafe. Cars are burning oil bc of it at low miles. I run 0/40 or 5/40 in any new engine.

 

[nate379]

For what it is worth, I have been running SuperTech 5w-30 Full Synthetic or High Milage Full Synthetic with a Motorcraft filter on my 2011 F-150 3.5 EcoBoost year round here in Anchorage Alaska. During the dead of winter our daily avg high is around 10 degrees F with a low around 0 degrees F. We can have cold snaps down to -35 degress F that last a few weeks or three. My F150 lives outside and doesn't have a block heater. Besides some slower cranking, which is more likely to be attributed to low battery voltage from cold temps, I have never had any issues. During the summer we move up to highs in the 70s/80s with lows at the 50/60s. I run the truck in excess of the Ford Algorithm. Typically I change it around "130 %" mark by resetting it back to 100% when the "oil life indicator" drops to 70%. I have to add 1 qt between changes. Each change is about 7500 miles. The truck currently is sitting just over 180K miles. The only major mechanical repair has been the transmission. Around 160k it was replaced.

It's never been -35* in Anchorage. Even -25* is rare, last time it got that cold was about 15 years ago.

 

[hank2]

A very long time ago, 1970's. For a 1968 Pontiac GTO, I used single grade 40 and sometimes, 50 racing oil. I was a fool. I don't know if that oil was even detergent. Pennzoil or QS. I did switch to QS 10w40 for Winters.

I stuck with the 10w40 year-round for a long time. I had an episode in Jan. 1981 during an insane cold snap in the part of Pa. I was living in. It was anywhere from -25F to -32F every morning for approximately a week. Not super rare in a couple of notorious cold spots in Pa., but unheard of in that area. A Fiat 128 that I commuted in long distance, would start but the oil light would not go out. I quickly quit trying to do that. It must have been chilled window putty. Oil was QS 10w40. Too cold for that grade, but there was quickly an uproar to QS from numerous places. Turned out they owned it due to a bad batch of QS 10w40. Some, like me, got some bucks for an oil change. Others actually got engine replacements. I switched to 10w30 after that, even if that had no better winter specs. 20 years later, I got on the 5w30 bandwagon.

 

[gfh77665]

Single wt. SAE 40 and 20w-50. Never mattered a bit.