Lawnmower oil?

the 5w30 will be okay, the multigrades cover a better range than the old SAE30 and SAE40 anyway.

if the mowers don't have an oil pump (more than likely they don't) then the perfect oil is non detergent, as detergent types are intended to scour/clean the engine and deposit the muck in the oil filter, whereas your engine relies on the oil and combustion bi-products to sink to the bottom of the sump.

if you really do want to use SAE30 though, you can buy it from Morris Lubricants as they specialise in lubricants for older type engines, but for my part, I find them expensive.

Paul.

Very informative ,never knew what the detergent thing was all about.
Chickened out in the end and bought 5L of Sae30 from Machinemart for £24 (ish) and as is always the way, found a Litre and a half I'd forgotten about.
Still, all ready for next year