I changed the oil on my truck last week before I used it to tow my race car. I have been using Mobil 1 20-50 for a few years and the truck has struggled with low hot oil pressure and a ton of leaks around the rear main seal/ oil pan area. I was getting my head around planning on a rebuild.

I couldn't find any Mobil 1 Synthetic, so I purchased some Castrol 20-50 dino oil to put in. All I can say is wow, , what a difference. The truck stopped leaking oil after a long freeway run, the engine is quieter and the hot idle oil pressures are higher (by a lot). I am very happy, but the problem around this is that I don't know why?

I have some ideas why, but I would like to understand if you guys have seen the same issues and results.

Eric

 

your dino oil gets into the cracks and sludges like its supposed to. synthetic doesnt do that, it does the opposite and blows out the sludge which allows the block to leak like a strainer

synthetic is a good oil for newer engines but i wouldnt dare put that stuff in my truck because i know it will turn into an oil puddle in my driveway!

 

funny my dads E350 did the opposite. he ran cheap oil for years, and when he switched to a synthetic the exhaust cleared up, no more burning!

but his engine was only 20 years old, not 35, and had low miles. that makes all the difference.

stick to standard oil until you rebuild.

 

Don't forget to use a zinc additive or you will ruin the cam with standard oil.

 

err... what? have yet to have heard of this... can you explain a bit on this?

 

New engines have roller tappets not flat tappets. Plus the EPA has mandated that the zinc and phosphorus additives be removed. These are both extreme pressure additives that help prevent wear.
The end results is flat tappet camshaft failure (especially on new camshafts) is at an all time high.
The only thing you can do is read whats in your oil. Find one that still has zinc in it.
Competition Cams has an informative posting on their website about this subject.

 

I don't know for sure, but was told by a mechanic once that synthetic doesn't burn the same way, as in white smoke, etc., but that it will make you cough if you smell the exhaust. He said a common trick at auto auctions was to fill them with synthetic so they wouldn't smoke. Breathing exhaust doesn't sound like the best idea, but I guess it's one way to tell.

 

Literature at the store reads something like this:
Synthetic Oil Doesn't Cause Leaky Seals & Gaskets - BestSyntheticOil.com

also have been trained that the molecules in the synthetic are actually smaller, and there fore far more prone to leak on an older engine.

Personally use the basic Castrol petroleum stuff and a quart of Lucas Oil Additive. I used to rebuild motors and just have seen some outrageous mileage when you change the oil every 3K. I like the detergent agents in Castrol too. It will eventually leave any engine just about as clean as it can be made to be and still function day to day. Tore down my wife's 175K Nissan GA16DE and found almost zero sludge anywhere. You could wipe the valve cover and eat out of it. It was a simply awesome after having worked on so many sludged up havoline and Quaker State engines.

As for filters: In depth filter comparison...
Engine Oil Filters

 

i run mobile clean 5000 conventional...since it's only 11 bucks for 5 quarts and i use vehicle brand filters like AC Delco on my cavalier and motorcraft on my fords...

that mobile seems to be pretty good for my car but i haven't had any real work to do to it yet to see the insides yet..hopefully never have to....we'll see how it does in my truck...

i have always heard that if your engine has been running conventional that you continue to use that because if you swap to synthetic you have to stay synthetic..in other words swapping oil types will hurt the engine.


but i must say i'm no oil expert...and i get confused about weights...luckily where i live it's almost always 10W30 or 10W40

 

After using CompCams breakin additive to break in the new flat tappet cam I run Valvoline ZR1 racing oil in my flat tappet trucks. It has the proper amount of zinc in it for the cam. CarQuest can get it by the case in 10w30 and 10w40. On the shelf they have 50w and 60w for the true race cars or high mileage engines.
In the roller cams engines I run synthetic blend (I like Pennzoil, but choose your own brand).

Mark

 

What's the scoop on Motorcraft 10w30 synthetic in a old 390 motor? Bad idea or good one? Today I just changed the oil with motorcraft and 1 quart of lucas. Did I screw up?

 

I run 10w40 Havoline in my 79 302 and 79 400 along with Lucas. I run 10w30 Rotella in my 73 302 along with Lucas. Other than that they don't get any special treatment and they haven't ate their cam yet.

 

Since I've been chassing oil leaks, I've been running the cheapest grocery store brand, or wally world moto tech stuff in my trucks... Over several oil changes, and lots run straight through, I can't tell any diference between it and havoline, napa, or shell oils, and I'm saving $$. I don't care what i is as long as its dino oil and deffinetally isn't synthetic... I won't even do a blend.

Dad had the oil changed in our 78 at a shop once and against his wishes they put a synhetic in it... this was mid 90s and synthetics were just becoming main stream as i recall, and there were a lot of horror stories going around... so we wanted to avoid the stuff. It turned out to be true; Too high of a detergent is my guess, and thin to boot. Wasn't a thing wrong with that engine before this. The oil pump went, it ate all the grime in the seals out and grooved the main bearings with it... engine blew in less than 500 miles. A lot less.

I'm *tentivelly* running a synthetic trans fluid because its literally all I could get, but its the only synthetic anything in my truck... Not bad so far.

A tip; don't ever get synthetic brake fluid, it will MELT OUT AND EAT all the seals in your brake system...(cutoff date is somewhere in the 80s *I think*, a change to newer rubber compounds)

G.