View Full Version : Royal Purple in a Datsun 5 speed.

04-24-2011, 11:02 PM
After having a hard time getting the plug out of the side of my 5 speed (I had to have it put on a lift in order to swing a large enough lever) I had the tranny drained of it's old fluid and replaced it with Royal Purple 75w-90 GL4/5. We all want to believe that we've made improvements when we do something like this, and I could swear that I had more power, but objectively?......

When I drive I watch the oil pressure and the temp gauge to know when the car is warmed up. After about 15 minutes the pressure has dropped to "normal" range. I hate to give #'s as gauges vary, and everyone knows what is right for their car, but when all warmed up and at speed mine runs in the mid 50's. Well, after the drain and fill I took it out and after about half an hour of running the oil pressure was still in the high 50's, a gain of 3 to 5 lbs..... the only thing I can think of is that the engine is working less hard, so not getting as warm, so the oil isn't thinning out as much, so the pressure stay higher. ....... hmmmmmm...... I just may change out the stuff in the diffy too!

04-24-2011, 11:10 PM
I'm confused....are you saying your engine's oil pressure has gone up after changing the tranny oil??

04-25-2011, 12:07 AM
It's not that its gone up. It's that it doesn't drop as much. ... It's still the same at start up, but higher than it used to be after running for a given period of time.

04-26-2011, 02:44 AM
I suppose it's plausible, but there are so many other variables that it's hard to do a controlled test, and casual observations are a good step down from that. That's especially important when the difference between the oil pressure you're seeing now, and what you remember, is small. It's likely that your oil pressure varies at least that much, depending on outside temperature, how hard you're driving, and similar factors. It might be that you're just now noticing it, because you're looking for it.

04-26-2011, 07:57 AM
Granted, it was ONE test, and not a scientific study. But it is a gauge I keep an eye on as it tells me when the car is warmed up and ready to GO. The difference IS small, but noticeable. I'm waiting for the rains to stop, or the Portland Auto Jumble for further observation.


04-26-2011, 09:50 AM
Yes Bill, but what my enquiring mind wants to know is...
Does the gearbox FEEL any different?

04-26-2011, 11:57 PM
I haven't had enough chance to work the box to know if it feels different. It's not balking, and the syncro's seem to work fine, but I don't drive it like I stole it, I drive it like a 50 year piece of machinery.