Had my 90k service recently, and since then, the operating temp has gone up about an average of 10 degrees C.

The needle used to hover a little above the 80 C mark, but now it seems more at home between 90 and 100.

It's been a bit warmer here the last couple days, but this is San Diego, so warmer means in the 80's as opposed to 70's. :^) Doesn't seem like it should make that much difference...

Oh, yeah, air conditioning on/off has little effect (and it didn't before).

Am I still within the proper operating temp range for the 3.8L V8?

Could a change oil viscosity have an effect on running temperature? The car is new to me, so when I did my first oil change, I had 10W-40 put in per the owner's manual. Its second oil change came at the 90k service, and they put in 20W-50.

What's the ideal weight for San Diego weather? (60-80F all year) The book's graphs don't help too much - almost all of the oils encompass the temperature range this car lives in.

I'm concerned because I'm getting ready for a trip to Las Vegas next week and do NOT want to be stuck with overheating problems.

Thanks in advance for your great advice. :^)

--Josh

1983 380SEL 87k mi

HMMM I don't think the service had anything to do with it. I think the warmer weather is to blame. My advise is to check the aux fan to be sure that it is working with the air on. Also check to see if the coolant is at proper level.

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Benzmac:
ASE CERTIFIED MASTER AUTO TECHNICIAN
SERVICE MANAGER FOR 14 BAY FACILITY
MERCEDES SPECIALIST 8 YRS
PARTNER IN MERCEDESSHOP.COM

Thanks for the reply, Benzmac.

I just had my coolant drained and refilled, and it's nice and full.

The aux fan (the one in front of the radiator, right?) doesn't kick on in unison with the A/C being turned on, but does turn on shortly thereafter (when the temp gauge gets above 80).

I guess it must be the weather that's affecting it, but here's my remaining concern: What will 110 degree F desert temperatures do to it?? I don't want to get stranded in the middle of Nevada, and would like to keep my A/C on throughout the trip. I have to imagine that the car was engineered to withstand such temperatures for a couple hours, but I just want to be sure that I'm in spec during normal conditions, so that when I push it to the limit, my temp gauge stays safely away from that 120 degree red mark!

Thanks,
--Josh