E32 740i - What Octane Fuel?

[markmullen]

Being the new owner of a nice old 1992 740i my thoughts came around to fuel, I filled her up on the way home and instinctively put 97 Octane in as I have always used Optimax / V Power, particularly in the Jap stuff I owned.

Then I started wondering, is the ECU in the 740 going to adjust itself to get the best from higher octane fuel? Am I wasting my money chucking good stuff in when I could put standard Shell in?

Also, I asked in General Gassing whether anyone had any views on which injector cleaner I should use, I was thinking being a 15 year old car a blast through with a cleaner might be a wise move.

Your thoughts and opinions would be welcome.

[Belleair302]

For the first 3,000 miles of ownership just use V-Power or BP Ultimate. See if the engine gets better and if economy improves. I would not bother about additional cleaners myself. The ECU I am sure will be able to cope and the engine will be happy with the better cleansers and additives in decent octane fuel.

[B'stard Child]

markmullen said:

Being the new owner of a nice old 1992 740i my thoughts came around to fuel, I filled her up on the way home and instinctively put 97 Octane in as I have always used Optimax / V Power, particularly in the Jap stuff I owned.

Then I started wondering, is the ECU in the 740 going to adjust itself to get the best from higher octane fuel? Am I wasting my money chucking good stuff in when I could put standard Shell in?

I've got a slightly newer 740 and run it on 95 for the majority of the time and don't notice any difference in performance or mpg when using V power or ultimate etc

Might just be me but it's not exactly a car I want to explore the outer edges of the performance envolope in (too big, heavy and expensive to repair is it all goes pear shaped)

The engine ECU will cope with a fairly wide range of octanes and as you say will adjust itself.

markmullen said:

Also, I asked in General Gassing whether anyone had any views on which injector cleaner I should use, I was thinking being a 15 year old car a blast through with a cleaner might be a wise move.

Your thoughts and opinions would be welcome.

Injection cleaner = spawn of the devil IMHO

Use decent branded fuel (not supermarket) and it should have all the detergent properties to keep the injectors happy for years

If you ever do have injector problems remove them and get them bench tested (with readings for output) and then ultra sonic cleaned then bench tested afterwards (approx £10 per injector and far more worthwhile than sticking "snake oil" type additives in the tank and believeing that it will work some miracle cure

Then you know exactly how much of a difference has been made to inj performance

What normally drives me to get injectors cleaned is poor mpg as the injectors spray pattern is compromised by varnishing from fuel with insufficient detergents - as a result they squirt rather than spray.