Penzoil?
 

Hey. I have an 83 GSL with 140k miles on the clock. Looking at penzoil 10w-40 conventional oil. Any experience with this or a better recommendation?

Asked and argued many times here Louis ;)
Everyone has a fav, but, dare I suggest one of the most popular choices "seems" to be Castrol GTX 10-30.... which I have used in my SA for the last 19 yrs (105K mi). But don't think there is a lot of, well, science to these choices. More important is (1) check levels regularly and (2) establish what your 'burn' is - ie how far you can drive BTW top-ups and change oil AND filter faithfully every 3K miles...

Stu A
80GS
AZ

I only use Castrol GTX 20W50 in my 7's. I have used this oil with zero issues since 1999. Mazda calls for 20W50 in warmer climates and weather and 10W40 in cooler climates and weather. You can go down to a 10W30, but either way I prefer Castrol oil. Likely nothing wrong with using Pennzoil. It's honestly personal preference. Here's am oil chart from an owners manual for your reference:



Attachment 746812

20-50 Castrol GTX here.

Its all made in the same refinery.

....and fish all come from the same sea, but I'll have Salmon instead of catfish.

Castrol has been in all my RX-7s from day one. I see you live where it gets pretty cold in the winter, so 10-30 is best until spring. Then maybe some thicker 20-50 in the summer.

Disregarding the facts of saltwater vs. freshwater fish... I'm also a long-time proponent for Castrol GTX and usually go 10w/30w; It flows like water in 120F summers, but I've never had any problems with lubrication (*knocks on wood).

Like the poster above, I don't think it really matters as long as you don't run out,

This is debatable but Rotella T6 or T5. I premix and don't have an OMP. I'll likely switch to something else sooner than later.

Oil threads never end well, but the original owners of my 12a '85 claim to have run 10w-40 Castrol in the car since new, and she's got 180k miles on her now. The car was in Oklahoma it's whole life, now it's living in Dallas.

I used to use Penzoil in my piston cars, then I did some top-end teardowns; the sludge buildup was ridiculous. Switched to Castrol 30 years ago, never looked back.

You want something that burns cleanly to prevent buildup on rotor faces, and that is thick enough to properly lube our high-friction engines.

I've been running my rotary on Castrol GTX 20w50 without oil-related issues for 30 years now. Wear has been acceptable, and buildup too.

Sythetics might be an option today, but they were considered rotary-verboten for so long I've never really considered them in the RX.