Are M54's (M54B25 specifically) okay with V-power / high octane fuels?

[Thrustyjust]

I used to own and I modded a focus St 5 cyl to over 320 bhp and would always use Tesco's or Shell high octane. I cant comment on making it any faster as that wasnt the reason for using super in it. It was to help prevent pinking and detonation.
I built a Westfield with a Honda S2000 engine in it. It was standard and designed for normal unleaded. It didnt justify the additional cost of super unleaded. Honda designed it to run on lower octane than we get at the pumps here. If I pushed it by tuning, with a supercharger etc, then I would have considered a better higher octane fuel.
I dont believe that the so called cleaners and performance gains are noticeable when used on my Zed , for the distance it travels .
A small snippet from a regular magazine write up............

Today petrol engines use similar anti-knock systems, but thanks to much faster processors in engine computers they can also use algorithms to predict when knock will occur. Naturally aspirated engines delay the point at which combustion is triggered (retarding the ignition) if knock threatens, all of which brings us back to the question of whether you need to fork out the extra dosh for super unleaded.

The answer is, there’s only one real reason to and that is because your car has a high-performance engine or the handbook explicitly says you should use it. Using fuel of a higher octane than your engine needs or can benefit from won’t hurt it, only your wallet.

The difference between premium and super unleaded at the UK forecourt these days is a maximum of two points (97 octane versus 99) and the chance of a modern engine being damaged by the lower of the two is nil.

 

[Smartbear]

The op was suggesting that engines can be damaged by using super unleaded though? I’ve never heard of that happening before :?
Rob

 

[MDUBZ]

There are several benefits to some higher octane fuels:

In addition to the cleaning additives Shell, BP, Esso (zero in some areas) use less ethanol in their premium fuels over supermarket fuels. Water in fuel tends to be a symptom of fuels with ethanol sitting for long periods of time, as the ethanol can absorb water. If you are leaving the car for long periods top up the tank and use a low ethanol fuel. You also get more sooting around the exhaust with higher ethanol fuels and if you have a plastic fuel tank it can cause them to swell. Older cars, and it's not a problem for Z4s, can suffer from perishing rubber components not designed to work with fuels with ethanol. E5 basically means ethanol content is between 0-5%. The regular fuels are E10 which can have up to 10% ethanol content.

In addition to it being a renewable fuel and cheaper, higher Ethonal fuels have the added benefit of lower engine running temps in theory.

Higher octane fuels are less compressible i.e. are designed to work with engines with higher compression; it's possible in a low compression engine it might cause some damage and could even reduce performance, but in an M54 I doubt it is going to cause any issues, you might get some performance gains and marginal range benefits.

I once had an issue with contaminated fuel bought from a supermarket; it destroyed the CAT and the engine never ran properly again.And whilst i received some compensation ~£500 for resolution of the issue despite them "in no way accepting any responsibility", I just won't go near it again.

Maybe i'm a mug but in my mini (mapped for higher octane), the ducati and the z4 (n52 3.0si) it's VPower only. The other car is a diesel (low/no compression) so apart from the occasional premium fuel for the additives, it drinks regular supermarket fuels.

 

[Smartbear]

So how could super unleaded fuel damage a low compression engine? Curious :?
Rob

 

[MDUBZ]

greater resistance to ignition i.e the fuel ignites later or doesn't. I think cars mapped to run in the UK are unlikely to have issues as the delta beaten regular and premium is not that big and the ECUs would sort it out.

 

[Anonymous]

I think the only time historically where higher octane fuels could cause a problem was in the old days of leaded petrol. The easy way at the time to boost octane was to add organic lead compunds..the higher the octane the more lead compounds..

These would come out as lead based solids and would be washed away with oil changes.

Higher lead petrols could leave accumulating deposits which could and in fact did clog oil feeds etc.

But they (outside of aviation) are long gone..so IMHO there is no plausible reason why no lead high octane fuels could damage a modern engine designed to run on unleaded fuels.

With direct injection engines such as the N20 and the N54 I'm not sure what the extra detergents are going to do save keeping the injector itself cleaner and/or the pipework to the injectors.

With manifold injection such as the OP car then there may be some extra benefits in cleaning the intake ports.

For the record, if you have an engine that has beem modded to use higher octane fuels if available they will give a modest boost to performance, but for stock engines designed for 95 max octane fuel the s/w and maps won't know what to do with that extra octane..

 

[Aulday]

Bloody ek never saw any of this due to post not auto subscribing! Will read through thanks guys!

 

[enuff_zed]

Too late! Your engine will be knackered by now

 

[GuidoK]

I work for a large retailer and we have around at least 4 or 5 tankers a week delivering all fuels,we sell a hell of a lot of fuel,dependent on where you get yours from may dictate how long they have had it,ours certainly does not sit in the tanks for long and thats all grades and fuel types.

That is interesting to know.
But I've heard from small retailers that premium fuels can sit longer in tanks and therefore age more. Where I live I can only get 98oct at a local unmanned discounter, so 98oct may be even less popular there (here the price difference is also quite a lot and people come there to get cheap fuel) But I've also heard that 98 octane (and higher) also are less prone to age. First because of additives and 2nd because 98+ is still ethanol free (where I live then).

For both the yay and nay sayers: I think it says in the manual that BMW only guarantees the listed performance if 98 octane is used (don't know if that's true). But I have a german manual. Does the UK manual also say that?

When my car was still stock I couldnt notice any difference except for maybe smoothness in very low revs somehow (which one would not expect, and see more of a noticeable difference in high revs).
For a tuned car (and then I mean supercharged etc, not a 10hp NA tune), 98 and above is the way to go. That's a no brainer.

 

[Mr Tidy]

For both the yay and nay sayers: I think it says in the manual that BMW only guarantees the listed performance if 98 octane is used (don't know if that's true). But I have a german manual. Does the UK manual also say that?

I can't remember what the manual for my E46 325ti said for the M54 engine, but the handbook for my E90 with the N52 says "Your BMW's engine is rated to run on Super Plus fuel Octane number 98. Fill up with fuel of this grade whenever possible so that the nominal performance and fuel consumption values are achieved."

Although it does go on to say if Super Plus isn't available it can be driven on anything 91 RON or above.

So it mostly gets Tesco Momentum as that is my nearest.

 

[Toed64]

This is an interesting topic that was discussed ad-nauseam on the BabyBMW forum. There was a lot of controversy and heated discussion there!

For years, my daily driver was an N55 135i with a few modifications. It was running between 370bhp and 390bhp depending on whether it had high or normal octane juice in the tank. The BMW ecu would turn the boost down a tad and run slightly more retarded ignition timing when it recognised that it was consuming the cheaper stuff. I was told this by the BMW specialist prior to booking a set up. He asked me to make sure it had the expensive stuff in the tank, if I wanted to see optimum numbers on the rolling road.

I don't know if the n/a cars adjust their ignition timing in response to the octane of fuel...and I was only convinced of the N55 story by the lead tuner at BW Chiptune...but there were plenty of contributors on the BabyBMW forum that concurred with his opinions.

 

[Ewazix]

.............. I don't know if the n/a cars adjust their ignition timing in response to the octane of fuel...and I was only convinced of the N55 story by the lead tuner at BW Chiptune...but there were plenty of contributors on the BabyBMW forum that concurred with his opinions.

I'm surprised the question splits opinions TBH. Octane is added to fuel to prevent damaging pre-ignition and maximise performance. Engines, including NA don't actually sense fuel octane but 'knock' sensors pick up pre-ignition and slightly retards the timing, this reduces max power and engine response (marginally). An engine will adapt to the maximum octane rating for your engine and provide maximum output, using fuel that exceeds the rating for your engine is a waste.

 

[enuff_zed]

Wifey's E85, M54 manual says:
" The engine on your BMW is designed to run on:
Super Plus/premium plus petrol - octane number 98 RON.
You can also run the engine on:
Premium grade unleaded petrol - octane number 95 RON
This petrol is also known as DIN EN 228 or Euro-Super.
The minimum permissible grade is:
Regular grade unleaded petrol - octane number 91"

 

[Mr Tidy]

That seems pretty conclusive then. If it's designed to run on 98 RON then Super plus is actually what it wants! One of those RTFM issues. :lol:

Although it can get by on anything above 91 RON.

 

[enuff_zed]

So if you nearly fill it with Momentum at 99, then add a little bit of standard 95, will that get it to the 98 it needs?

 

[Toed64]

.............. I don't know if the n/a cars adjust their ignition timing in response to the octane of fuel...and I was only convinced of the N55 story by the lead tuner at BW Chiptune...but there were plenty of contributors on the BabyBMW forum that concurred with his opinions.

I'm surprised the question splits opinions TBH. Octane is added to fuel to prevent damaging pre-ignition and maximise performance. Engines, including NA don't actually sense fuel octane but 'knock' sensors pick up pre-ignition and slightly retards the timing, this reduces max power and engine response (marginally). An engine will adapt to the maximum octane rating for your engine and provide maximum output, using fuel that exceeds the rating for your engine is a waste.

Opinions were only really split about whether the high octane fuel was worthwhile in the n/a cars and the old arguments about the merits of Shell V vs Tesco M.

I'm old enough to remember retarding the ignition on my dad's Alfa to cope with 4 star, when 5 star (100 octane) was withdrawn. My ears were finely tuned from then on...my own knock sensors! A friend of mine has a 1934 Lagonda. It seems that people in 1930s were expected to know what to listen for - it has an ignition advance-retard on the steering wheel.

 

[enuff_zed]

It seems that people in 1930s were expected to know what to listen for - it has an ignition advance-retard on the steering wheel.

These days it seems to be a reversed baseball cap that signifies a retard on the steering wheel!

 

[Toed64]

It seems that people in 1930s were expected to know what to listen for - it has an ignition advance-retard on the steering wheel.

These days it seems to be a reversed baseball cap that signifies a retard on the steering wheel!

:evil:

 

[Smartbear]

It seems that people in 1930s were expected to know what to listen for - it has an ignition advance-retard on the steering wheel.

These days it seems to be a reversed baseball cap that signifies a retard on the steering wheel!

That probably reduces performance more than any timing adjustment could
Rob

 

[Aulday]

Well I'd written a full reply but coming back looks like it didn't submit! But the consensus including my own opinion is to stay on the good stuff