I just purchased an SRT roadster from a private party and found a receipt from an oil change shop that shows synthetic 5-30 was used. This was not an oil change done at the dealer. It took place 2 1/2 months ago and 3,000 miles ago. Will I be ok with this different rated oil, or change it out ASAP with Mobil 0-40? I live in Las Vegas and it's still very hot here. Thanks.

 

If it's fully synthetic it should be okay. I was talking to my petroleum engineering friend and said there isn't much difference between 5w30 weight and 0w40 weight oil, just a slight difference when in cold temperatures. The kinematics viscosity is slightly different at 100 degrees celsius for each oil, but I wouldn't worry about it.

 

Ya, you should be fine. The diffs are only for temp differences. If you drive the car with low coolant on a hot LV day at 115 degrees and keep it floored for hours, then you might have an issue. A trip to the grocery market and back won't make that big a deal. Change it to 0-40W next time around, unless you want to be overly **** about it.

 

Though others might disagree, I would have the oil traces in the motor
totally flushed, if the 5-30 was from a company other than Mobil. My dad
was a horse trader (automobile wholesaler) for about 40 years, and I
worked with him for several years. One thing he was adamant about, and
I came to agree after experience, never change the brand of oil in a car
without doing as complete a flush as possible.

I've been told that the reason for this is that different companies (Mobil,
Castrol, Pennzoil, etc) use different additives, and some are not
compatible with others. If there is enough mixing, you can gum up your
engine it the oils have incompatible additives. Though the problem will
not display such symptoms as re-fusing to start, or seizing up, you
will lose performance, and will find that you need to change your filter
more often.

So, do what you want, and listen to who you wish, but I would recommend
a power flush before putting the Mobil One 0-40 back in. Then again, my
info may no longer apply in today's technologically advanced motor. But,
I still follow the rule, and I've got two vehicles with over 1/4 million miles
on them that have never smoked or leaked (oil pressure is higher in a
gummed up motor as the traces are blocking up like the arteries of a
person with bad cholesterol problems). And, none of those miles were
easy cruising. When I'm ready to go somewhere, I'm ready to get there,
so I drive hard.

Coyote (just crossed 50k miles on the SRT-6)

 

Thanks for your concern Coyote. It was Mobil One 5W-30 total synthetic but I changed out to Mobile One 0W-40 yesterday. It already had 3,500 miles on the last oil & the previous owner didn't reset the FSS so it was screwed up anyway. Now I have the proper oil and the Service System is set up correctly.

 

Synthetic to synthetic oil is pretty compatible, though true, there's a slight difference in additives. The only reason I'd be very concerned is if a non-synthetic oil was put in there. when non-synthetic oil is mixed with synthetic oil it has a tendency to form little globs of goo.