Synthetic Oil Change Interval

[conedodger]

All flat tappet engines apparently need zinc additive ZDDP. A few of the synth oil alternatives have this in appropriate quantity. Royal Purple being one. In the dinosaur oil category, Brad Penn, which is named for Bradford Pennsylvania and used to be the Castrol GT green oil before that plant was shut down has the appropriate ZDDP content. Now having said this, I think the most important time for this ZDDP additive is when the engine is breaking in the cam. This happens in the first 20 minutes at 2000 RPM. I have seen Porsche motors eat their own cams when not appropriately broken in, this in the first 1000 miles.

Changing oil every 3000 miles is very old-school and not necessary. Oil has changed. It is better and worse. The old stories about synth causing leaks while true, have been eliminated by changing the formulation of the synth oil. The ZDDP was taken out of most oils to increase the life of catalytic converters.

I change my oil twice a year. This frequency increases when I do track days with one or the other cars but I would guess miles to be about 750 - 1000 between changes. I do this only because oil that sits in low mileage cars can form acids that cause damage. I am allowed with my 'Historic Plates' and by my classic car insurance to drive 2500 miles a year each. I'm doing maybe half with each the 914 and the Z.

A friend who runs a performance shop and does routine maintenance on BMW, Audi, Porsche and Ferrari and such, uses 1000 miles per quart capacity with modern oils. He uses and recommends a Swepco Synth blend I think...

[Dr. 240Z]

I just spoke with a Quaker State 'Fluids Rep' about their synthetic, 'Ultimate Durability', and its use in older engines. Basically, he stated that it does contain ZDDP (800ppm) and that the addition of more ZDDP might be appropiate. That said, he did caution that the addition of excessive amounts of ZDDP can destroy certain types of catalytic converters.

I have learned a lot on this topic via your comments - Many Thanks

[71Nissan240Z]

valvoline vr1 racing oil is pretty good stuff.

[siteunseen]

Valvoline VR1 for the rebuilt 280, Castrol 10W30 GTX in everything else. 297,000 on a '87 Nissan Hardbody pickup, 240,000 on a 2000 Toyota Camry, 1000 hours on Briggs & Stratton Vanguard powered Exmark mower. Replaced timing belt on the Camry at 175,000, timing chain will hopefully get done this winter on my truck. No other problems just maintenance stuff. I don't like to buy new cars. Just bragging a little bit, thanks!

[ta240]

I personally think the actual oil you use doens't matter but how often you change it.

Years ago I worked at a farm that sent off oil out of every truck and tractor to be analyzed at every oil change. I talked to the guy that ran the testing place one time for quite some time on the phone when we were looking at different types of oils and additives and his recommendation was the same as yours. It isn't as important what you put in it, just as long as you change it frequently.

And it was for the same reasons listed here, oil gets a lot of bad stuff in it when you run the engine and you don't want the concentrations of that to get too high.

We had a late 80s Pontiac that I pulled the valve cover on at around 120,000 miles (we got it at around 110,000) and it had layers and layers of cooked on crud on all the insider surfaces. I have no idea what they used in it or how long they left it but it was ugly.

When we got our first brand new car it had a little tiny oil filter and only took about 2.5 qts or oil per change and it got a lot of in town driving and not a lot of miles overall so I changed it every 3,000 miles and did use synthetic but here is the top end of it after 100,000 miles:

and I never ran any sort of flush or cleaner through that engine. That kept me a fan of the regular change.

I just run the GTX 20-50 in my Z but it is old and original. And I change it twice a year and average about 7,000 miles a year on it.