Motors Premium fuel

I am glad I have a nice story to tell since the last time the petrol debate came up...

A friend of mine swore by Shell V-Power in his 1.6 Astra and when his girlfriend took it out she kindly filled up the tank for him (from empty*), he was annoyed and said his car felt horrible because she had put in regular, fair enough I thought. She was not convinced so we hatched a cunning plan...

So the next time she filled it up, again from empty, I told her to put in regular and tell him she had put in V-Power. He was saying to me "I can tell she put in V-Power this time, it feels so much better than when she had it before".

So me and his girlfriend thought this highly amusing but kept it secret for a few more weeks so she could fill it up with V-Power and tell him she forgot and put in regular. Again he complains of his car feeling sluggish and getting worse MPG.

If a car is designed to run on Premium fuels, then run it on Premium fuels. If not stick to standard. From what I have read it seems the biggest difference is between brands, different additives used produce different results, and for different people.

*Now I know changing fuel over the course of one tank isn't the best way as there's always quite a bit left over, but if anything it proves the point further.

 

The fuel's all the same; it comes from the same wells, tankers, refineries and tanker-trucks. The difference is in the additives the stations add; if you believe their marketing a long course of use will clean your engine from the inside out, dissolve carbon deposits, get you greater mileage, solve the situation in the Middle East and make Keira 'Twice' Knightley appear in your bed. In practice, all of the road tests I've seen (and that's been a few) have given inconclusive results and none have shown clear benefits of any particular brand. The higher octane stuff works in theory - anyone who's ever suffered American 87 octane knows what I mean - but like the others say, it's a minimal difference between 95 and 98RON.

Also, correct me if I'm wrong, but don't modern cars recognise knocking, and are capable of advancing or retarding their timing to take maximum advantage of their fuel? I'm pretty sure our 'performance car' does, anyway.

 

The higher octane can be used on old engines that need leaded petrol. By that theory, you could use regular fuel and use the lead replacement stuff to reduce knocking at higher compression

I use diesel, don't have to worry about namby pamby is my fuel good enough As long as the injection system can cope, a diesel will burn just about anything...

The supermarket fuel can be cheaper as they put more biofuels in, which are taxed lower.

 

Family member works for an oil company.

 

I do use premium fuels.
I can notice the difference between premiums in the high (5.5K RPM Plus VTEC range), but low down, barely.

I also get varying MPG depending on brand. Shell V-POWER for example giving me some of the best, and Tesco Momentum 99 the worst.

Mankz: &*$%£"$&"?$"$"£ FUFUFUFUUFUFUUFUUFU

 

I definitely used to notice the difference in responsiveness between shell optimax and regular fuel when I had the Type-R. My mate who thought we were mad for paying for premium petrol admitted he noticed a difference when he put it in his scoob. It's also worth noting that standard fuel in the UK is slightly high octane than elsewhere anyway.

 

Questioning the performance is one thing, but it's a lot harder to question maths. I have a record of every fuel purchase I've made since mid-2007

I measure economy and fuel price, as well as fuel type, on a spreadsheet. V-Power is 7p a litre more expensive than regular Shell (I wouldn't use supermarket fuel irrespective of vehicle unless I really didn't care about the car). For me V-Power equates to an improvement in fuel economy that negates 5p of that extra 7p. So it's costing me 2p more and feels subjectively nicer, plus I'm helping my baby last when she's already done 149k and still pulls like a train and starts first time, every time.

It's all very well mouthing off about it either way, but if you're curious try it for a few tanks and see what you notice. If it's not for you, it's cost you a few quid at most. Whatever you do though, don't rely on the inaccurate trip computer readings.

 

No, the way it is measured is different. US 89 is UK 95. They use the same system the UK uses in Japan, and they generally run 100 as 'standard'...

I've seen a 110 pump once or twice before

 

EVO magazine did a fuel test at one point on three different cars, of various fuels, and ran a dyno on each.

On a modest hot-hatch, there was naff all difference between standard and premium, however on a balls-out rally slag (Think it was an FQ400), there was a significant difference in peak power and torque, think it was 10-15% improvement on each front.

I always used to think there might have been a bit of a difference on my last car (Citroen C2 VTS), though I eventually convinced myself that it's all in my mind.

I'm driving a diesel now, and always fill up with the premium stuff. Mileage is probably a bit off from the standard stuff, though the engine sounds and feels smoother (could be in my head though). What's definitely an improvement though, no black soot spewing out all over the exhaust - win.

 

Tesco are supplied by Shell
Sainsburys are supplied by BP

BP fuel is like water, don't touch it unless you have to

you CAN tell the difference if you go from having some BP fuel in to getting some proper jungle juice from Shell/Tesco.

that's even in my corsa.

My mate had a mk1 Focus RS, you had to put a minimum of 97 octane fuel in it as they don't have knock sensors.

Also i think i'm right in thinking that European fuel is higher quality than american base fuel which is 92/93 octane?

 

In the states they use AKI not RON to measure octane it isn't the same scale, 95 RON = 91/92, 98 RON = 93/94.

My car should only run on 98+RON if I can only get 95 I have to flick a switch in the arm rest and I get even worse MPG.

 

Surely the simple answer is if your car has a knock sensor then yes there is a slight difference, if not then using a higher octane fuel than recommended is pointless.

 

Almost correct, it's right now

 

The difference between 95 and 98/99 RON is significant. You can advance the ignition further without det to gain extra power, this is true in a knock limited engine.

Give this a read: http://www.megamanual.com/begintuning.htm

 

I'll occasionally have a couple of tanks of super in mine, but mine is a 17 year old car with a 40-50 year old engine design, . Not sure if I can feel the difference, or notice any economy improvements (my right foot is too heavy anyway, ).

My dad only puts super in the TVR, put normal in and theres a very high change you can get detonation (as its basically a race engine, the speed six).

It'd be interesting to see some dyno results from normal and super on a low powered modern car. I'm sure fifth gear must have done it, they've done pretty much all the other things (like power boost stuff, which does nothing).

 

I know that, butwe're talking about consumers here, not engine designers.
How many people "advance their ignition" manually?
How many engines LET you manually advance the ignition?
Who has access to a device to reprogramm their engine management?
Sure, most engines have knock sensors now, but they're used for detecting low quality fuel or similar mishaps, not for active re-tuning your engine.

For Joe Public in a Golf* out there, the statement "there may be a slight difference" is the trueest one.

*or similar, built to run on RON 95, like most average cars.
If you know what you're doing and have the means, yes the difference can be bigger.

 

My Citroen C2 wouldn't tell the difference if you pee'd in the tank. My dad's Noble however, you can tell the difference between normal fuel and premium. Much more responsive, and lasts longer.

 

Yeah, I agree. I was just trying to point out that the fuel can make a big difference. Manufactures will be very conservative with timing they really don't want det.

 

I think you guys might be experiencing a larger difference on how old the fuel is. If you get your fuel from a place that doesn't sell fuel quite as often as another place, their fuel is generally much older. So some of the volatiles in the fuel have evaporated away which will affect your cars performance.

But this premium fuel gives you a better mpg, or more performance isn't placed in fact. What determines octane rating is not the quality of the fuel. What does is the ease of combustion for the fuel. A higher octane fuel takes a lot more energy in order to get the fuel burning in comparison to a lower octane fuel. The reason why a higher octane fuel is important on high performance engine is easy, it's all about the engine knock. engine knock isn't a enlightening term. A better term would be "pre-detonation" they call it knock since the engine tends to make a "knocking" sound when it's taking place.

In a properly operating engine, as your cylinder is compressing the fuel/air mixture it reaches maximum compression, then ignites the fuel using the spark plug, and it creates a pressure wave which radiates away from the point of ignition, evenly applying force to inside of the combustion chamber. In an engine with pre-detonation, as your cylinder approaches maximum compression, the pressure causes the fuel to randomly ignite some place other than the spark plug. To add to the problem, soon after you get an unwanted ignition, your normal spark-plug driven ignition takes place, creating two different pressure waves in your cylinder. These then collide with each other and reflect most of their combined energy into either the piston top, or the top of the combustion chamber. This tends to do wonderful things to your engine like blow chunks of metal out of your piston. Not a good thing.

So to counter act this, they make fuels that require more energy to begin combustion, effectively "less flammable" these fuels are called high-octane or high-RON or whatever octane rating you use. Thus making it less likely that you will get a random ignition in your combustion process.

So the short of the story is, only buy premium if you are experiencing engine knock, or run a high compression naturally aspirated engine (~10.5:1 or higher) or have a forced induction engine with a reasonable amount of boost pressure.

That additive junk contributing to cleaning out your engine is mostly marketing spin, as the only thinks I could see them adding is unwanted refinement byproducts, and then calling them "engine cleaning additives". If you really want your engine to be a bit cleaner, consider perhaps an after-market fuel additive, or a high quality oil like Royal Purple or the like.

 

I have not seen any performance difference on premium to standard fuel in my car. Although if the price is the same I'll put premium in just for funzies... Never have owned a car that needed anything other than standard fuel...