Synthetic oil and STP

[redcar]

I usually use STP oil treatment at every oil change, is it ok to mix with Synthetic oil? My 03 Impala has 115K, and my 01 Yukon has 118K. Thanks

[maxwedge]

There is no reason to thicken your oil with STP, the point of the synthetic is for better cold start flow, additives are not recommended,.

[j cAT]

Originally Posted by redcar

I usually use STP oil treatment at every oil change, is it ok to mix with Synthetic oil? My 03 Impala has 115K, and my 01 Yukon has 118K. Thanks

this STP additive was used widely many years ago ,,,usually on worn engines using alot of oil....it also had the problem of [in cold climates] not fully draining out,,,and causing a lot of debris to stick to the internal engine crankcase...

I would not recomend the use of these additives in these newer vehicles,,,,the engine you have is designed for a thinner oil..
stp would reduce the synthetic oils from doing their job ...which is to reduce wear and friction.....

[redcar]

Thanks Again guys, once again great info!