Mixing synthetic and regular oil
 

Hello all-----Is it ok to mix synthetic and regular oil?

Rich

Re: Mixing synthetic and regular oil
 

Yes, several oil companies sell it already mixed. I use NAPA brand in my Lincoln

Re: Mixing synthetic and regular oil
 

Hmm. Interesting to hear this. Back in my snowmobiling days, it was a definite no-no. Nobody ever gave a good reason, though.

Re: Mixing synthetic and regular oil
 

One requirement for an oil to meet a standard (such as SJ, etc.) is that it has to be compatible with all other oils meeting that same standard.
There were a lot of myths and misunderstandings floating around in the early days of synthetic oil. Much like with the zinc "issue" today.

Re: Mixing synthetic and regular oil
 

NAPA's synthetic blend!

Re: Mixing synthetic and regular oil
 

Same weight and type, no problems mixing.

Re: Mixing synthetic and regular oil
 

Motorcraft 5W20 synthetic blend, recommended for my wife's Explorer.

Re: Mixing synthetic and regular oil
 

I was just getting ready to post what Bob posted! Ford recommends a blend on their newer cars.

Re: Mixing synthetic and regular oil
 

It doesn't even have to be the same weight.

Re: Mixing synthetic and regular oil
 

Thanks for all the excellent responses.
Rich

Re: Mixing synthetic and regular oil
 

Agree.

Is it also a myth that once you use synthetic you can’t go back to regular? I assume yes

Re: Mixing synthetic and regular oil
 

I've read the opposite. They say going synthetic on an old dirty conventional oil engine can cause leaks because of the cleaning action synthetic is good at. And I experienced that myself first hand. I bought a O/T car with 200,000 miles and put about 10,000 more miles on it. Then I switched over to Royal Purple and lost a cam seal within 1,000 miles. Bad luck, just a fluke...? I don't know, but that's why I'm hesitant to put synthetic in my flathead.

Re: Mixing synthetic and regular oil
 

But your flathead doesn't have lip seals like your modern car (unless it has some modern adaptation, in which the new style seals should be made for use with synthetic).

Re: Mixing synthetic and regular oil
 

I ran Mobil-1 20W-50 in the original engine in my '51 before I put the new engine in. I didn't see any increased leakage while I was using it.

Re: Mixing synthetic and regular oil
 

Here we are talking oil. I've read if you have a dirty engine don't use synthetic as it bonds to dirt and can clog the works. Now seals and synthetic? I've used what was cheap.



I think most use oil that is cheap and change it. I could probably use corn cooking oil in my car for 1k miles and probably be fine if I changed it back.



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Re: Mixing synthetic and regular oil
 

Make of car and year varies. My VW modern car requires "full" synthetic oil.

Re: Mixing synthetic and regular oil
 

If you have a turbo (My F150 3.5 Ecoboost has 2) it is better and recommended to run the synthetic as it doesn't "coke" on the shafts like non synthetic oils will due to the heat involved. I don't run synthetic in my flatheads as they seem to mark their territory enough as it is and I don't want to chance worsening that.

Re: Mixing synthetic and regular oil
 

I have been doing it for at least 15 yrs now. At one time synthetic was expensive. no more.
I would always make sure there was at least 1 qt of synth in my car, because it will save your engine, should it run dry for any reason.


walmart sells 5 qts of synth for a little over 15. at this point and it is a moot point, if worried about cost.


I run it in my lawn tractor, A's and all cars and vehicles. nothing better.

Re: Mixing synthetic and regular oil
 

Saw a TV show not long ago were a few old cars were driven across the country. One of the old cars was a Ford flathead. This show was sponsored by Shell Oil. The flathead Ford driver said Shell ran several test to determine the best oil to use in the flathead for the cross country trip. The oil Shell provided to the flathead drivers was the synthetic mix 10W 40. Just my 2 cents worth.

Re: Mixing synthetic and regular oil
 

All motor oil is compatible. That's an SAE requirement. Since I have a '40 with no lip type main seal, I run straight 30W Rotella. That 10w, etc. wants to drip out the rear. 30w doesn't. No freezing in San Diego so it's fine. You can mix weights, synthetic, etc. No problem.