oil pump question
 

hi all i have a v 3/4 impreza and i am just going through the motions of a full service including c/belt and so on, the question is i am going to change the oil pump for piece of mind but i see that there is 3 types 10mm 11mm 12mm, do we know what the difference is, much appreciated jays

pm david at API engines he is a trader on here. He knows his stuff on oil pumps.

10mm is the standard one for your car. The 11mm and 12mm ones are only needed when the engine requires more oil flow i.e. AVCS. Fitting the larger pumps to your engine would not help since the extra oil pump flow is wasted creating heat through recirculating the oil through the relief valve.

^ This is your exactly what we'd recommend. The only other time you may consider upsizing the pump is with a built motor that has larger bearing tolerances with higher rev limits.