Amsoil Signature Series Vs. Royal Purple Vs. Penzoil 5w30 Motor Oil

Z1107

New member
Since we discuss this so much on the forums Im making this review to help people decide on a good choice for motor oil. I ran Penzoil in my Rex when first got it as that was what the dealer used, car ran normal nothing special. On my oil change I switched to Royal Purple... pure crap. The Rex idled harder and ran harsher, huge difference. So I ordered Amsoil Signature Series from Jordan based on everyones recommendations. When I drained the Royal Purple it was already broke down and nasty after only 1200 miles. After 340 miles of Amsoil I noticed a significant improvement, the car idles and runs so much more smoothly which seems to get better. At 500 miles I noticed a small fuel mileage improvement also. Now Im not trying to say that royal purple is terrible for all cars (my roommate runs it in his built Cobra w/no problems) but I would not recommend it for a turbo'd car, just runs like shit. It cant handle the higher temps.
 

HolyCrapItsFast

Drinks beer!
I've been saying this about RP for ever... I never jumped on the band wagon when everyone else did because there was simply no proving data out there. I did try it once and had exactly the same experience you had... I will say it is crap.

I only ever use Amsoil or RedLine anymore. Nothing in the world beats those oils.
 

IGOTASTi

System Operator
Staff member
I only use Amsoil products. They have been around forever and been tested over and over again. I use nothing but them.
 
I run Redline heavy in my transfercase and rear end, both are stock and haven't failed yet. Trans gets OEM fluid usually but right now has Redline MT90 due to availability.
 

Vermont

New member
I ran Royal purple when I first got my STI. At the start of 2011 I moved over to Amsoil due to all of the oil analysis that were put up on line.

Honestly the majority of the filters on the market are made in three different factories. The worst being Fram filters made by Honeywell up in canada. These things are pure crap. All american dealerships (as far as I know) use these filters, just with a different label on them. Cut open a Honda, Subaru or Ford OEM filter and you will see that the construction of the internals is exactly the same. Back in 2008/early 2009 you used to be able to buy the JDM filters at the Subaru dealership (which are Bosch made btw) but not any more. Next quality wise above the honeywell brands, you have the K&N, Mobil 1, and Bosch. Which are all made by Bosch, over all good quality and I have yet to hear of a problem with them. I honestly don't remember right now who makes the filters for Amsoil or those other higher rate brands and I am not even sure if their quality is any better than Bosch but I do know that they usually cost most than a few bucks more, so dwell on that.
 
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