Royal Purple has dynos showing gains but on much larger engines. Lil 4cyls like ours dont have that much surface area to loose large amounts of power to friction (in the engine, trans is a diffrent story) I use it because its better than most oils in many other ways. I think I saw maybe 1mpg to .5mpg gain after switching to RP 10w30 and RPs Max Gear. :ermm:
There is supposed to be a lower coefficient of friction and are also more likely designed for high heat/rpm applications. The 'racing' oils are just a teeny bit better performance wise but be careful as they may be too 'thin' for normal engines doing normal driving.
I personally use the recommended viscosities from Hyundai(there's a reason they use this specific type of oil in the first place as they have tested the engines for hundreds/thousands of hours and get proper protection!) but stick with quality brands(BP Visco 3000) and not cheap K-mart stuff.
Motul, and other specialty engine oils, can and do make a noticeable difference in engine performance, even on our little 4bangers, though it comes more down to feel and tractability then raw outright horsepower gains. Last season I used several different oils and mixes throughout the season in order to find what I felt was working the best.
Before I sold my silver miata, I ran an event with 5w40 Shell Rotella Synthetic. While I think the higher viscosity helped protection and the oil lasted extremely well, it also hurt how rev happy the motor was and it was much happier with 5w30.
I used MotorCraft Synthetic Blend, 2 qts 5w30 and 2qts 5w20, in the Hyundai when I first got it. I think things ended up too thin and I used a good bit of oil while autocrossing with this mix. It felt fine on the street however, so this combo (or maybe straight 5w30) would be fine around town but for hard racing use the blend doesnt hold up.
I then switched to what I think my favorite mix was: 3quarts of Mobil1 5w30 and 1qt of Redline 5w30. It revved extremely smoothly and felt outright the best and lasted the longest of the oils I used last season (in terms of discoloration). Its what I'm going to be running this season in the red miata, if/when I ever get around to changing the oil on it lol.
At Nationals, I used 10w30 Royal Purple. It seemed to do very well, about as well as the M1/redline mix, so if you want to buy cases of 1 oil only I'd go with it, otherwise I'd do the M1, redline mix again. It does take some getting used to to pour purple oil in though lol.
Whatever ANYONE does with oil in their engine,the viscosity ratings are very important. For example a CG13DE powered Nissan Micra I drove when 17 needed 5w30 and using any thicker oil would damage the engine(the nissan specialist mechanic I used has rebuilt a few with people buying cheap 20w50 brands),the oil journals were too thin to flow thicker oil safely and efficiently. If the oil is too thin you can have added 'clatter' and also some areas protected by 'oil spray' may have insufficient oil as it can move from these areas faster(being thinner) and again cause issues. As Skierd said above,the engine used oil when thin(burnt by the engine most likely due to oil getting past the piston rings and burning off.
Two different engines will more than likely have different oil requirements due to design more than anything,like newer high tech engines have finer castings and more sophisticated designs which probobly do need thinner oil whereas the 12valve accents have engines based on old Mitsu technology and would probably be damaged if too thin.
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