Can thicker Oil Rais compression and increase Vac?
 

well hey guys, i was wondering, i have 10w-40 in my fc and it seems to run fine, i might have a vac leak somewhere because im only running about 35mmHg which is about 10-12. I was wondering if running somthing like 20w30 could increas the compression and increase vac due to the thicker oil. sorry if this is a stupid question but id thought i put my question to the test, thanks -alex

i doubt it would help your problem. as a side note, the first number of the oil, ie 10w or 20w, is the heat index. the second number is the weight. 20w30 is actually a lower weight (thinner) oil than 10w-40.

oops thanks for the correction. i couldnt remember which way was which

This is a little off topic, but I would strongly recommend against running 10w40. It has way to many viscosity enhancers to be running in any engine. unless it is getting below 20 degrees F, you should be using 20w50.

Take a look here for more information

http://www.vtr.org/maintain/oil-overview.html

- Cooper Lacy

About the only advantage to running 20-50 over 10-40 (other than the lubing and viscosity advantages) is that, **sometimes**, you will see less smoke out of an engine that previously smoked. More so on a piston engine than a rotary. Hell, sometimes, just by changing oil BRAND you can make the oil seals swell and seal a bit better, resulting in less smoke if you had a smoke problem previously.

BUt yes, unless you live up north (during winter) you should run 20-50 in the rotary. Especially at this stage in it's life. I run 20-50 in all my vehicles year round with no issues at all.


OIl has no effect on vacuum or compression of a rotary, or any other engine that I am aware of. Both are functions of seal/housing wear (or ring/bore wear for a piston engine), and of course condition of manifolds, gaskets, and hoses in the case of vacuum readings.

just curious with using a thicker oil. i used some of that bardual(sp) no smoke thingy in my car recently and it seems to feel much better now. that bardual stuff was as thick as molasses. would a thicker oil have a similar affect.

well that stuff will end up ruining your engine since our cars naturally inject oil from the pan into the compression chamber for lube.

So you may have added more carbon deposits by doing that.

This is partially why there is a debate on using synthetic oils.

Although the Royal Purple guy almost sold m on switching since he said his stuff actually burned cleaner than reg dino oil.