Oil.

"Dave Plowman (News)" gurgled happily, sounding much like they were saying:

Take a look at Carlube

If the engines are in good nick with decent oil pressure why not do them a favour and switch to something more modern like a synthetic or semi synthetic 5/30? You'll get better cold starting and quicker engine protection from cold and fuel consumption should improve.

My last fill was with AC Delco fully synthetic 5/30 at only £10 a gallon from a factor that a mate in Aberdeen uses. I could ask where and what the current price is.

There's no doubt in my mind that with the higher film strength of synthetic oils you get better engine protection even with much lower viscosity oils than you can achieve with mineral oil. You also eliminate that black sludge of death that plagued cars in the 90s and earlier when heavily worked mineral oil baked into carbon.

I used to strip down Fiesta XR2 engines, which I built a lot of, that had the rocker covers and top of the cylinder heads half filled with carbon deposits to the point that the cam lubrication oilways were often completely blocked. You just don't get that anymore with synthetics. 100,000 mile engines can look almost brand new inside. Just a sort of light greenish gold sheen over everything.