Share with me some opinions on the use of synthetic oils (Castrol, Royal Purple, etc.). - Expense aside.

I have a 1978 F100 with a remanufactured 302 with a few hundred miles on it. And I have two other vehicles with 100-200 thousand miles each.

Is the synthetic a waste on the motors with high mileage? Will less tolerance of the older engines mean leakage with synthetics? And whatever other issues you may wish to mention.

Thanks for any info.

CB3

 

The rule of thumb I have been told (and always followed) is that a high-mileage engine that has used conventional oil all its life should not be introduced to synthetic oils because the synthetic oil (by design) can penetrate into tight areas, leading to leaks or pushing around sludge that may not have otherwise happened with conventional oils.

A brand new motor would be a different story.

 

Not all synthetics are created alike. Mobile 1 and maybe one or two others are full synthetic and many are blends... which do not need to be labeled as such.

A major benefit is the synthetic takes heat longer/better than a conventional oil without breaking down. Hard running without oil cooler would favor synthetic.

I run synthetic in my DD's with the longish factory change intervals. Before I ran conventional with shorter intervals. My last Durango I traded at 160k. It ran as new with the same oil consumption as new (1 qt per change interval) running Mobile 1.

In my Dent I run diesel engine oil to get enough zinc for the flat tappet cam. That's not a consideration for a roller cam engine, however, diesel oil is available in synthetic.

As far as leakage, any change in oil type may promote leakage in a higher mile engine... synthetic included.

 

Vintage engines that have not been rebuilt and run on conventional lubricants should stay with conventional oils. New engines, race engines, and engines rebuilt with tighter tolerances are OK to use synthetics.

 

I agree, that is what I have always been told.

I have also heard that old valve seals do not like synthetic oil. I have actually heard that the old rubber compound would get damaged by synthetic oils. Not sure if that is true or not, but i heard from an old school mechanic.

 

BTW, there is a lot bad stuff going on around royal purple. Turns out that their special "oil additives" do more harm than good. I believe there are actually some law suites against them because of it.

 

Synthetic in the 302 yea....the two high mileage motors no....for the very reasons mentioned above.

 

Thanks everyone for the info.

CB3

 

Welcome to the forum, CB3

Blue and White, your info regarding diesel bears looking at for cost comparison. I have been using ZDDP Plus in Valvoline 10W-30 conventional oil since I saw it advertised in the NPD catalog and read up on the benefits of zinc in our flat tappet engines. Sure ain't no Cadillac converter under my old truck...

 

Unless you can find some kind that has reasonable amounts of zddp at a reasonable price I wouldn't use it in an older non roller engine. All off the shelf syn has very low zinc and zinc additives don't mix well with syn oils. In a older engine the seals and gaskets can start leaking also.

 

I've started going with this oil : Schaeffer Oil | Synthetic Motor Oils, Natural Gas Engine Oils for Diesel and Gas Engines based on farmer friends input. Several farmers around here run it 100% in all their equipment, because it helps seal the engines up. It's really thick and one of them runs it in all their trucks, especially the high mileage ones. Just my .02

 

ok ,even if we have our motors rebuilt shouldnt we be using the ZDDP,or is that just break in,and then synthetics? revised Thanks Mike "Our engines need ZDDP regardless of new, old, rebuilt. It doesn't matter."

 

I was always told not to mix dino and synthetic oil. If you've been using dino oil, stick with it. Not good for your engine to suddenly change, like the people above said.

Now if you're doing a complete rebuild, it's totally up to you. When I got my 460 built up, I used synthetic. Better penetration, less likely to break down, etc.

If we start talking about syth oils for other things, like transmissions, that's a different story. Unless the transmission you have requires FA fluid, or ATF+4 (chrysler ****), a good oil to use is Valvoline MaxLife. It's designed for high mileage transmissions, and works in either standard or synthetic applications.