STP oil additive between changes?

I usually put a container of STP in my TR3 between oil changes. Anybody else do this or am I just old school?

Depending on which oil I purchase I will add a bottle of STP to add ZDDP. I don't add STP to the oil between changes though.

I am "old school" allergic to STP. Possibly they have changed the formulation by now (they didn't use to advertise ZDDP content), but it used to create huge amounts of sludge in the oil pan. Vivid memories of scraping it out with a putty knife. On a TR, it tends to fill the rocker shaft with sludge, too. Some people like sludge (it's kind of like grease, helps quiet the engine and so on) but I don't.

I am also very suspicious of the concept, that one can full of additives can "improve" any oil; when I know the oil makers spend literally years tweaking their additive packages to optimize a whole bunch of parameters (like sludge formation, ash and so on) and each oil is different.

So my strong preference is to buy an oil with the characteristics I think I want and then not add anything to it. I have always had excellent luck with Valvoline products; I'm currently running their synthetic "racing" 20W50, which already has plenty of ZDDP and viscosity improvers. (Old school STP was primarily a viscosity improver.)

YMMV of course

The only car I remember adding STP to when I pumped gas in high school were the original Vega's when they were burning oil.

Scott

TR3driver said:

...I am also very suspicious of the concept, that one can full of additives can "improve" any oil; when I know the oil makers spend literally years tweaking their additive packages to optimize a whole bunch of parameters...

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Agreed. All oils are formulated and produced to very tightly controlled standards. It doesn't need any extra help. Imo.

Mr. Granatelli was a great promoter and marketer and supporter of motor racing. But, snake oil is still snake oil. Then again, I'm of the same mind about BG, Lucas Oil, Sea Foam et al.

Dale said:

Then again, I'm of the same mind about BG, Lucas Oil, Sea Foam et al.

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And they haven't even been slapped down by the FTC ... yet.

<span style="font-style: italic">According to the FTC, the defendants made numerous false claims in advertisements regarding the engine protective qualities of their oil additive -- "STP Engine Treatment with XEP2."</span>
https://www.ftc.gov/opa/1995/12/stp.shtm

I agree that 30 years ago STP had a reputation as being nothing but snake oil.

While modern oils are formulated to a high standard and should not need additives, many do not contain ZDDP. The ZDDP content in STP is now prominently displayed on the front of the bottle and I do use it when I buy an oil (like Castrol GTX) that no longer has ZDDP. I don't always have access to oils like Valvoline VR1 which do. So I stand by the statement I opened with that I add the STP during an oil change if I need ZDDP. I do not add it for its thickening properties or other ingredients.

I cannot comment on the observations about sludge except to say that when I was first tearing down engines I found sludge as described not on engines that had STP in them but engines that ran Penzoil and/or Quaker State. To this day I will not use those oils.

In closing, I did not bring up ZDDP to start another thread/argument about whether it is needed or how much is needed and who provides the best formulation. I only mention it because ZDDP is the only reason I add STP.

I was adding the "red" bottle of STP oil treatment marketed for 4 cylinder engines as it provided ZDDP and its viscosity was substantially less (thinner) than the blue bottle. The "red" doesn't appear to be available anymore and so I've gone the ZDDP in a bottle route.
I stayed away from Valvoline Racing Oil as being a racing oil it is non detergent which is fine for racing where the oil is changed frequently but I have difficulty accepting that application for a street car.
Re: Pennzoil/Quaker State. I remember many years ago switching from Pennzoil to Castrol GTX. The oil never seemed to get dirty with driving with the Pennzoil, after switching it would with the Castrol. My conclusion was that the Pennzoil wasn't holding the dirt particles in suspension and they remained in the engine. That concurs with the sludge build up that was noted.
Bob

I can't remmber if it was Auto Zone or O' Reillys but one of then had this on the shelf. Not nearly as thick as STP
https://barsproducts.com/catalog/view/22-engine-oil-supplement-with-zinc-treatment-4401

Bob_Muzio said:

I stayed away from Valvoline Racing Oil as being a racing oil it is non detergent

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There are actually several different kinds of Valvoline "Racing" oil. The "Not Street Legal" stuff is low (not non) detergent, while VR1 and VR1 Synthetic have normal detergent levels and, in fact, meet the API requirements for grades SM, SN and SL.

I too used to add the "red bottle" STP between oil changes in hopes of boosting the ZDDP level (maybe just psychological). It's no longer made but STP just came out with a High-Mileage type in a grey bottle. The "Bobs the Oil Guy" site did a test and the ZDDP was about the same as always. Their conclusion - probably increases viscosity, but ZDDP...not so much.

Jeff
74.5 & 75 TR6

What do you make of this in regard to viscosity and oil pressure and STP use: I was coming back from a British car get together at a racetrack about 50 miles from where I live. I did some spirited laps around the track in my TR3 and headed for home later in the day.A very hot day and about a 50 mile trip. I noticed that the oil pressure gauge was reading 60psi and I was going about 65-70mph. Normally the gauge reads 70 psi out on the highway. Seeing as I was about 25 miles from home I remembered I had a bottle of the blue STP in the boot.The oil level was still on the mark. I put the STP in and continued on. Soon the gauge was reading 80 psi and remained there the rest of the trip. Did the STP thicken the oil to increase the oil pressure or is my gauge wonky?

IMO, STP is snake oil, but it keeps my steering box from leaking!!

karls59tr said:

Did the STP thicken the oil to increase the oil pressure

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Yes, exactly. Now, if your experience is similar to mine many years ago, you'll find that the effect fades in 2000 miles or so and the STP winds up on the bottom of the pan.

When you switch to Valvoline synthetic oil can you just drain the old oil or do you have to flush out the engine before switching to synthetic?

I've never flushed when switching to synthetic. No apparent problems. On one non-Triumph, oil consumption dropped markedly immediately after the switch, while with all my TRs it has remained about the same.

However, the current TR3 does seem to be tapering off a bit on oil consumption. Not sure whether to attribute that to the VR1 synthetic, or the upper cylinder lubricant I've been using, but I am definitely happy about it.

I used to put STP in back in the day when I had motors with low oil pressure. In those days I didn't have the skills/tools/money to do a engine rebuild. The STP did increase the oil pressure for a while, although the effect seemed to wear off over time.

I used those "fix in a bottle" products because I couldn't afford the real fix, I have since come to the same conclusion as many of you, and don't use them.

Will also add that the sister of a girl I dated in college (early 80s) worked in a repair shop, she said the same thing as Ransall, the stuff sludged up the motor, don't know if that is still true. She thought it was crap.