Oil for HOT weather

Its oil change time and just wondering if I should switch to something heavier than 10-30 for the summer. I'm here in AZ, so its usually 110 + during the day.

THX

At the temps we see in the PHX area, I would not hesitate to use 20W50 for the summer, for sure. Just make sure it's API certified to the latest standards, and you are good to go. Synthetics, with their greater heat tolerance, are a good move, too.

*shrug* I run 20w 50 year round here in So.Cal. Never really had a problem with it.

-Scott

For temps like that I'd recommend 20W50 if you run conventional oil, or 15W50 if you run synthetic.

For that matter, in summer you could easily use straight 50 weight racing oil.

castrol gtx 20w-50
been running it for years...not during below 30 degree weather!!!
thinking about going to mobil one,

anyone know the mileage diff. between changes for conventional vs. synthetic?

xjhm said:

anyone know the mileage diff. between changes for conventional vs. synthetic?

Click to expand...

If you read the fine print, almost any normal use of an XJ fits the factory criteria for "severe duty," so the recommended oil change interval is 3,000 or 3,500 miles, not the 7,500 miles they talk about for light duty. I always changed oil and filter at 2,500, partially because I felt it was cheap insurance and partially because it's easier to remember multiples of 5,000. I never burned off enough in 2,500 miles to add a quart, so it probably evened out in the long term

My brother is a service manager for a BMW dealer. BMW's recommended service interval using synthetic is 15,000 miles between oil changes. I kind of figured if BMW can warrantee their engines with a 15,000 mile interval, I could certainly switch to synth and run a 5,000 mile interval. That's what I run. I switch my '88 XJ and '88 MJ to Castrol 5W50 and I change the oil and filter at 5,000 miles. I'm sure I could go out to 7,500, but so far I can go 5,000 w/o adding, and if I try to extend it to 7,500 I'll have to add a quart at $5 per quart, which will partially offset the saving from the longer interval.

The factory has never issued a recommended interval for synth as far as I know, so you're pretty much on your own.

20w50 is a bit excessive. 15w40 will be more than enough, and will give you better gas mileage over 20w50.

Thx for all the ideas. I've been using 10w-30 valvoline changed every 3000 miles. Last summer I ran 10w-40 and when it started getting colder(i call 60 degrees cold), my oil pressure was still w/in factory spec, but higher than I like it, so I went to 10w-30 and everything went back to normal.

So I guess I'll run 10w-40 and not worry about it.

THX again.

There will be no problem running 10w40 year round. That's what I do. 10w30 and 10w40 are the same thickness when cold, and that's the only thing that matters as far as a "winter" oil. 15w40 would be better for the summer, and then 10w40 in the winter, because 15w40 won't shear down as much when it gets hot.