The Stovebolt Site Forums The Shop Area Engine Shop using STP Oil Treatment as a supplement for ZDDP ??

Has anyone have any thoughts about using STP Oil Treatment as a supplement for ZDDP in their oil ? The bottle says it has ZDDP in it but I don't know how much.

Way back in the dark ages, I used STP as an assembly lube on engine overhauls. Every engine I built that way had some sort of oil-related failure and didn't go the expected distance. Just to prove to myself that it was just a coincidence, I built one more engine with STP. That one stuck the oil pump relief valve open and trashed a crankshaft. Now I wouldn't put STP in a lawn mower with a rod knock!
Jerry

Bought a 87 F150 5.0 that had 105k miles from a guy that had it since new. I kept the same oil change regimen he did. (Mobil Del-vac 15w40 and a bottle of STP) Don't ask me why I just done it. With a name brand filter, Motorcraft mostly. When rust finally ate up the truck to where you could not drive it anymore the engine had 367k miles and still going strong. Just sayin.

I worked for awhile in a small independent shop. We had a costumer that wanted a can of STP put in his car with each oil change. We had to pull the pan for some reason and there was about two inches of gunk in the bottom of the pan. I don't put it in anything I own.
Jim

I have used STP for assembly lube for decades. Best thing in the world if you aren't doing a rebuild and reinstall to run in 48 hrs. Everything else will run off in no time, you can take the engine apart weeks later (without running it) and there is still a coating of STP on everything.

With newer engines running tight tolerances and new oil technology, I've stopped running additives at all.

When I had a fleet of rental VW Vanagon campers (water cooled)in the early 2000's, I always used used STP to rebuild, but with the first oil change I would add a teflon additive like Tplus or T-fal I think were the names.
That got a lot of customer abused buses home, badly overheated, low on oil, pushed to the limits, that normally should have stopped running.
The engines I bought for rebuilding had been through the same thing but they had spun bearings, seized pistons etc.
Just my experience.

We used to sell a lot of STP to people with old worn out engines. It quietened them down, cut down on oil consumption and raised the oil pressure. We even used it in our old GMC gassers and 855 Block Cummins engines to make a few more trips until we overhauled them. It needs to be added slowly with the motor hot and running. Otherwise a blob of it will settle in front of the oil pickup and starve the engine for oil. I think it has kind of outlived its usefulness, but it kept a lot of old engines going a little while longer back in its heyday. I still use ZDDP on flat tappet engines. My father sold an oil that had zinc in it. It was something that was developed during the war and was way ahead of its time.

Like posted above, I've seen STP save a few old worn out aircooled engines (VW). As a youngster I remember one of the mechanics at the FBO I worked at using STP for a continental aircraft engine overhaul. Approved or not for aircraft it was his choice, he said he's the one signing off the paper work.

Used STP mixed with 2 qts of 30wt oil in every old mower engine I brought back to life from the scrap pile. Every one started on the first pull and I never had to add any oil to them again. Sold hundreds of those old mowers for $25 over the course of 4-5 years.

I had always heard STP wasn't good to use in air cooled engines... Go figure....

John

I don't have any doubt that STP used to have its place, but I wouldn't be surprised if it has been reformulated to the point where it doesn't do our old engines much good. My short answer would be to use a flat tappet additive and my long answer would be to go to the Bob is the Oil Guy forums (BITOG). They will have you enrolled in undergraduate chemistry courses before long :)

I've got an old can of STP from the 60's sitting proudly on a display shelf in my shop. Theres one of those stainless steel punch-funnels laying beside it. They are a constant reminder of the good ole days to me. I punched many a can of oil & STP into all kinds of engines when I was a gas jockey back in the day Mine are for display only tho....

There are several modern oils availble that contain ZDDP at close to old time amounts and there are also ZDDP additives availble to add to your regular oil. I'd go one of those routes for ZDDP.
Dave

You do not need to add anything to modern oils for flat tappet motors. Its a myth that you need it, and even back in the day ZDDP was added to prevent oil oxidation, not to reduce wear. Initially it was, but the uber high levels (1000ppm+) were not for wear or tappets, but for controlling oil oxidation. This is straight from GM engineers and the report is readily available online.

Modern oils have taken out ZDDP and replaced it with other additives. Modern overhead cam engines still use flat tappets... and millions of flat tappet motors are being made today.... from I-4s to V-8s.

Nothing you add to your oil will stop wear. If you want to do something to slow down wear, get a pre-oiler. Its a documented fact that 90% of wear occurs at start up. Pre-oilers get the initial oil film created much sooner than the oil pump.

Please do go to Bob is the oil guy.. they will back up what I have said.