Hi guys and gals,
I am wanting to start using synthetic amsoil in my high milage (212,000 miles) F-150 4.2L. Best I know, it has always been run on conventional oil. My cousin and mechanic said that since it has been ran on "thicker" conventional oil for as long as we know, the seals would leak with the "thinner" synthetic oil. Of course I'll use the same SAE (5w-20), but the way I understand synthetic oil's chemistry is that it has smaller particulars than regular oil. Bottom line, can I switch safely from conventional to synthetic on a high mileage engine?

Thanks a ton or should I say a 1/2 ton truck
-SweetPete531

 

SweetPete531, I'm going to have to side with your cousin, switching to a new type of oil that your vehicle isn't " built " for may cause you some problems; especially being that you have 212,000 mile on the engine already. If your engine is running off the recommended oil and you're not having any problems I wouldn't risk changing oil.

 

Camparishdy, What do you mean by my engine isn't built for it? I do agree though... I'm not going to risk running synthetic until I'm absolutely sure it's safe. My grandpa is an Amsoil dealer and I thought I'd try to help his "oil dealing hobby".

 

SweetPete531, Your question about the engine not being built for synthetic oil inspired me to research some research and based off my findings on fordparts.com and a few other respectable pages and I learned that Ford actually recommends that you use synthetic oil over conventional oil. Im sure the reason your cousin said that the gaskets and seals would probably leak is based off of earlier types of synthetic oils ( I based my opinion off that as well) but that was like 20 years ago when synthetic started to really kick off. With the advances in engineering tech synthetic oils have been manipulated on the molecular level so that it is indeed 100% better than conventional oils. Ford released a study a few years ago on conventional oil -v- synthetic -v- synthetic blends and said nothing bad about synthetic oil besides being a little more pricey, little was said about the synthetic blend besides that the blend has impurities in it due to being blended with conventional oil, hints "synthetic blend" and of course conventional oil came in last because it has the most impurities and the rate you have to change conventional oil out. Ford did say that changing to a synthetic oil on higher mileage vehicles would benefit because of the purity of synthetic.

 

sweetpete; you do it and it'll leak. Guarantee.
But first, it's very impressive to have 212,000 miles on a 4.2L. I would continue using what the previous owner used if that can be determined. If not, use 5W-20 Motorcraft Synthetic Blend.

 

That is very helpful Camparishdy, Thank you much. Amsoil it is then. 1saxman, I am also impressed with my truck's mileage on this engine. It make me wonder if it was ever overhauled...

 

Just an fyi......
With regards to syn vs non-syn oils, today, all oils are considered synthetic. While I am not promoting this company nor their products, they have an excellent, detailed description as to how & why all oils today are considered “Synthetic” Synthetic Motor Oil and was confirmed through legal proceedings http://www.scribd.com/doc/217558103/...s-Day-in-Court. Mfgs such as castrol, are actually using a oil base that is not by previous industry standards to be even considered a "synthetic", was sued (By Exxon/Mobile IIRR) and they won in court because they were able to demonstrate with additives they were essentially delivering a syn product. When looking at all the refineries in the US (2014), the only one really capable of supporting 100% synthetic oil manufacturing is Chevron/Phillips refinery in Texas…and it is not promoted as a synthetic oil.