I have always used mobil 1 blue cap (5w-30). I am about to do the 37500 service and I started to ask myself, at what point, if any, do you switch oil to like a 10w-30 or something else as the engine ages. is mobil 1 5w-30 good enough for the life of the vehicle? 60K, 80K, etc.

I currently live in Tampa and lived in San diego before that, where i purchased the car back in 03. I'm sure if i move to a colder state i may need something like 10w-30 or whatever cold weather calls for. Appreciate the help.

 

The critical part of oil viscosity is the extreme hot idle oil pressure [accurately measured after an hour or two interstate cruising say when you pull of ramp at the first stop light.

15 psi is the minimum [synthetics will have a tiny [5-10%] bit lower oil pressure than conventionals [due to the more homogenous molecular sizes in synthetics base oils].

I used 10w30 [90 Q45] until around 270,000 miles a shift to 10w40 solved some minor issues.

You need a large very accurate gauge to reslove +- 1-2 psi down at 15 psi.

A very good use of time is to attach the accurate gauge and graph the oil pressure vs coolant temperature from a cold start until warm up , just crank and log every 30 seconds at idle [log rpms also as they will be high for 1st 5 minutes.

Then log the oil psi in increments to study the bypass pressure of oil pump and filter.

You will see that the oil filter new vs middle vs used gets progressively worse [goes into bypass] at lower and lower rpms as it dirties up.

 

I use M1 10-30 here in Phoenix. The dealer said they recommend it for hot climates. I do the changes myself but I wanted to check with the dealer to be safe.

 

Q, i think you went a little too technical for me man. I think i got more confused now. I was just trying to see if at a certain point you would switch oil to prolong the life of the engine, if that is necessary.

 

I used Mobil 1 synthetic 5/30 for the first 10K and
replaced it with 10/30. Since I live in Ca our weather
never gets that cold. Don't worry, just switch it can't
hurt a thing!

 

stick with the 5w30...im on 64k miles and have been running royal purple 5w30 since 1000 miles

 

Thanks for the replies, I believe i'll stick with the 5w-30 for a while longer.

 

I've been using Amsoil's AMO 10w40 with excellent results... I'm going to perform a used oil analysis soon.

 

I live in sarasota just south of you and im at 81,000 miles and i still use 5w30 mobil 1 synthetic....

-sean

 

Did you know our cars come from the factory with 10w40 oil? Also... the only drawback of the 10w40 is slightly lower fuel economy.. which I've yet to notice.

 

Mobile 1 is no longer a true synthetic, they are a group 3 now like Castrol syntec and Pennzoil Platinum.

Current true synthetics are Amsoil, Redline, and Royal Purple.

The one I use is German Castrol Syntec 0w-30 (autozone only) Unlike the other Syntecs it is a true synthetic. Available for $5 too. I have seen great use oil anlysis on the VQ35 with this oil.