Best oil/weight for RX7 running in the SE

[Shannon1530]

I was just wondering what is the best oil/weight/dyno/synthentic combination for a car participating in ITA/IT7 events in the SE?

[Mike Guenther]

Several years ago, the late Karl Sloan, who was a highly regarded rotary engine builder in the SE, told me to only use Valvolene VR1, 20W50 oil in a newly rebuilt engine I bought from him. It was a 12A motor and it ran very strong. Karl recommended fossil oil over synthetic in rotaries because it is mixed via the oil metering pump with the fuel and burned.

I have used VR1 in a couple of 13Bs and piston motors too, ever since. Bought a case yesterday.

I change my engine oil and filter after every race weekend. I use Purolator Pure One filters.

[Mike Spencer]

I'm no expert, but FWIW I have been running the Valvoline VR1. Only I've used the 10W40 (when I could find it). The oil pressure in my 12A normally crests 100 psi under load, so going to 20W50 seems a little counter-intuitive.

In the North Carolina area it's getting harder to find 10W40 so I've been pondering what to go to next. All my fellow IT7 racers seem to run something different, so I really don't know what I'll be using in 2008.

Watching this thread with great interest....

[CaptainWho]

When we got our first RX-7, the owner told us he only ran Shell Rotella T 15W40, so that's what we ran. We had several folks concur with that choice afterwards, so we've stuck with it. I wouldn't want to go up much higher on viscosity, since we get 100 psi easily at race RPMs with the Rotella.

[tom_sprecher]

Valvoline VR1, 20W50 in crankcase. Belray, Motul or Klotz in the gas at 80:1.

[C. Ludwig]

I like the Rotella T synthetic. But I also prefer to premix. If you are using the injection then stick to dino oil. If temps are an issue straight weight oils should run a few degrees cooler.

[Chris Wire]

I like the Rotella T synthetic. But I also prefer to premix. If you are using the injection then stick to dino oil. If temps are an issue straight weight oils should run a few degrees cooler.
[/b]

Chris, I've heard differing opinions on running dino vs. synthetic, but usually only from users, not engine builders. The builders tend to recommend only what they sell, so it's hard to get what I believe is a straight-up objective opinion.

What differences do you find when you tear down a dino motor vs. a synthetic motor, and what does the injection have to do with your recommendation if you're premixing anyway?

[C. Ludwig]

Chris, I've heard differing opinions on running dino vs. synthetic, but usually only from users, not engine builders. The builders tend to recommend only what they sell, so it's hard to get what I believe is a straight-up objective opinion.

What differences do you find when you tear down a dino motor vs. a synthetic motor, and what does the injection have to do with your recommendation if you're premixing anyway?
[/b]

From what I have seen engines that premix seem to come apart much cleaner than those that inject. Carbon build up is much more noticeable on injected engines. Most of what I've torn down though that has been pre-mixed has been either my own engines or engines that I know well what was run through them and those have all used Red-Line synthetic 2-stroke oil for pre-mix @ 100:1. Depending on what model and the condition of the pump, lines, injectors you may be getting a much larger dose of oil than needed at times...or none at all. Injection is just a crap shoot IMO. If injection wasn't a band-aid to allow secretaries to drive a production rotary you wouldn't see someone like Jim Downing pre-mixing gas at an event.

As far as bearing wear it's hard to say. Honestly I haven't been through enough engines of different useage to develop a real good opinion. Good clean oil would seem to make the most difference. I've torn down 100k mile stock engines with bearings that were trashed and some that look brand new. Difference? Has to be clean oil. Just tore down a 70k mile 3rd gen engine a few weeks ago that came from an automatic car. No way you can over rev it or otherwise abuse it. Bearings were junk. Housings looked great for the mileage though.

I like synthetics in the race engines because they've been proven time and again to offer less friction and to be more stable at high temps. It's a win-win. For street cars where ultimate performance is a secondary issue I'll use dino oil.

I think the biggest thing as far as reliability is to keep the temps in check with proper cooling and keep fresh oil in the sump. Do that and I really think the name on the bottle the oil comes out of won't make a hill of beans bit of difference.