Brand differences - is LPG like petrol?

[gazchap]

I know it's a conscientious topic, that being whether supermarket petrol is worse than the "premium" brands like Shell and BP, but I'm wondering whether LPG has similar "problems."

I used to have an E46 3-series that I ran mainly on Morrisons fuel, occasionally Shell/BP if on a motorway. Everything was as happy as Larry, until one day I put a tankful of ASDA petrol in. After about 20 miles, the engine management light came up on the dash. I left it as it was as the car wasn't noticeably different, and it remained on until a few days after I'd emptied that tank and put other fuel back in (I think it was Shell) at which point, the light went off.

I now have an E65 7-series that's been LPG converted. Haven't had it long, and it was converted before I bought it (a Prin system, which are apparently one of the better ones)

I ran it on petrol initially, and then found a local LPG supplier (not a petrol station, a domestic gas merchant that also deals in LPG) and started running it on LPG. After a day or so, the engine management light came on and stayed on. I had the codes cleared at a friendly garage, and they came on again shortly after. Had them cleared again, and this time switched the LPG off and have been running on petrol ever since, with no lights on.

So, the question is, if I put Shell LPG back in after I've empted the "local" stuff, is there some sort of additive in Shell LPG (which is what the previous owner used exclusively) that would stop the light coming on? Are some brands of LPG different to others?

[RockyBalboa]

No major differences in LPG except that in the UK it's mostly if not all propane and a mixture of propane and butane in Europe.

[Oldandslow]

AFAIK LPG is LPG. If you want to run on gas you need to get your installation checked out. Maybe it's never been right. At least get any codes read to where the problem lies.

[Liquid Tuna]

Oldandslow said:

you need to get your installation checked out. Maybe it's never been right.

This. I've had LPG cars before and I'd have thought it's far more likely to be an issue with the installation or system itself than the quality of LPG.