Oil type after engine rebuild

[chilipalmer]

Hi

I'm about to rebuild my Puma engine. I have a question about the type of oil I should put after everything is done. I've always used 5w30 but the mechanic told me it's too thin and that I should use something else like 10w40. Since I'm changing a lot of stuff, wont a thicker oil harm the engine given that the compression rate will (hopefully) go up?

 

[JPTipper]

The engine is designed to take 5w30 semi synthetic, your mechanic's probably assuming "old car=thicker oil"

 

[chilipalmer]

The truth is that even one of the guys from Ford told me to use a thicker oil when I told him the car was burning oil. But now given that the engine will get new rings and whatnot I'm not sure it's a good idea to use 10w40...

 

[Wild E. Coyote]

Stick with 5W30 as Ford intended

 

[stumc]

a heads up for you mate, be wary of where you get your big end bearings from. almost everywhere lists the 40mm versions for the 1.25/1.4/1.6 for the 1.7 aswell, and theyre different. im in the throws of trying to find a suitable alternative. ive just ordered some from a random mitsubishi engine from eurocarparts. theyve been special ordered and theres no part number for them yet, but if theyre correct, theyll be listing them as a puma part. the main bearings they list are correct though.

if you intend on changing the oil pump be prepared for a bit shock, as theyre NOT cheap.

just be warned.

 

[PumaNoob]

Are you talking about oil to bed the engine in or to run the engine on mate? To run the engine in then 5w30 is better, but if you are to wanting an oil to run after bedding in, if you are planing on abusing your car, then a slightly thicker oil will be better for a few reasons (only my opinion). Your car with the supercharger will mean engine temps are higher then usual, meaning viscosity is thinner at higher temps, meaning less protection then intended. So what i have used is a 5w40. the first number is flow at cold temps, and the second number is a flow rate at 100 degrees.

So on cold starts, you dont want something thats too thick, especially where VCT is involved. A cold engine regardless of power output would be best with OE reccomended oil. But if you are going to run your car hotter then manufacturer intended, then it makes sense that you want oil viscosity at OE reccomendations even at your increased temps, so you need a thicker oil at hot temps to compensate.

i know of people running thicker oil in occasional track cars with no issues.