Race Engine Forum UK

About two more weeks and the engine of my Lada Samara (1500 8V, 2xSolex C40) will be ready to run (expect a new topic in Readar's Cars soon). The enigne has done 160 000 km, probably always on mineral oil (lately Liqui Moly 15W40 with MoS2). It has a new crankshaft, piston rings, camshaft, valves, lifters, modified head. The only old parts lef are the pistons and connecting rods (I hope I am not messing anything in terms of vocabulary). And the question is: on what oil should the first kilometers of breaking-in be done?

I found your tip, Guy, on this forum recommending mineral oil for new engines' break-in. Can I consider my engine new? I am quite confused cause searching through the internet I found contradictory opinions: that it should be always done on mineral oil because with synthetic oils the friction is not big enough. Or that it should be done on the same kind of oil the engine is supposed to run on later on (in my case fully synthetic 10W60).

Please help me on this one cause it would be a ridiculous thing to waste all the time and money consumed on this project by choosing the wrong oil.

Use a mineral oil like Castrol GTX 10W/40 for break in. No-body overloads an engine during this critical phase, that's why you don't need a race grade oil with upper temp viscosity rating of 50 or higher. Use light load only and use the gears freely. These days I prefer to recommend about 300-500 miles during bedding in although blocks honed with FlexHone will actually bed in on a dyno within 1hr. In a car however, it's equally important to test out the 'whole installation' really so that is why I'd really take longer over it, and did a while back with a new V8 engine in my wife's Range Rover.

There are semi-synthetics which work fine during bedding in, but rather than list them all I'd go with the oil above or equivalent. If you try to bed-in an engine with synthetic oil it may never bed-in at all!

The only exceptions are engines with coated bores and rings eg: nicasil, which don't bed-in (by friction and mating wear of ring against bore) in the old fashioned sense.

Hope that helps,

GC

Thanks a lot. This does help, surely.