Do I need to use high octane fuel?

J

Jiminwatford

Member
The previous owner and a few people have told me I need to use high octane E5 fuel

My car is a 1973 V8 and I was told it is a higher compression than one which followed soon after

Could this be the main reason for using E5 or is it just because it's an older engine

Does it need it for protection or just to maintain maximum performance?
 
I use E5, or the Esso stuff as apparently it contains no Ethanol, not sure whether I believe it though.

Ethanol, (the E in E5 or E10) isn't good for many engine parts including fuel lines and parts inside your carb, so best avoid it if you can.

Bit pricey though :confused:
 
To get the best out of any fuel your engine should be tuned for it. With modern EFI with O2 sensors and knock sensors the ECU can sense pre-ignition and retard spark to avoid damage, and then advance it again when conditions and fuel permit. In my turbo Suby I run 98 Octane,and around town and the economy is pretty average, but on a trip the improvement in economy more than makes up for the extra cost. So, if you advance your timing until it pings under load, then back it off a bit until it is quiet, you will have optimum timing ON THAT FUEL. It will be up around 10d BTDC . If you have to fill up with a lesser octane fuel, be ready to relaxx your right foot.
 
quattro said:
Ethanol, (the E in E5 or E10) isn't good for many engine parts including fuel lines and parts inside your carb, so best avoid it if you can.
Click to expand...

This seems to fit with what i remember that the E5 offers more protection. So it's not the higher octane per se but the reduction in ethanol wihch is the benefit
 
Hi, From what I understand the E5 and E10 is the maximum percentage of ethanol that is permitted. It varies from from company to company how much they use but is typically half the permitted level. Ethanol is an octane booster so improves power but not economy. It can attack parts of the fuel system components most notably rubber hoses, you need to have R9 (external) or R10 (submersible). You need to get it from a reputable dealer by Gates or Cohline, there's plenty of counterfeit hose about, if they can fake the hose they can fake the printing. Another problem is that it's hygroscopic so soaks up water and can then separate from the petrol. The car really needs to be kept in use to stir it up.

Colin
 
E10 vs E5 is less likely to pink, but its economy will be a little poorer. where petrol's optimum mixture is in the mid 14s (parts of air to parts of petrol), ethanol/methanol is down in the 7s. E10 should have an optimum mix ratio around 13.9, where petrol is 14.7.
 
Here in Australia, there are two ethanol fuels in either 91 or 94 octane. I have not used either in my Rover. Prior to 2007 when it retained the original 3.5 litre 10.5:1 engine, I had the ignition timing set to TDC @ 600rpm, and I used 97 or 98 octane fuel, the highest that I could buy readily. It always pinged. I did try an octane booster from Repco and that worked, the pinging disappeared and the engine pulled much better, but it was expensive.
With my Rover's 4.6 litre engine which has an 8.37:1 CR, I use either 95 or 98 octane with the ignition timing set to 12 degrees BTDC @ 600rpm and for almost all forms of driving that I do, it does not ping. I can make it ping if I try, but I choose not to. The engine delivers reduced fuel consumption this way.

Ron.
 
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