95/99 Ron - Strange results

[Fox1429]

So,

I've had my GTI for 6 months and covered 4000 miles.

I've run my car on Tesco momentum 99 since new and have always got 320-330 miles from a full tank.

A few weeks ago I was stuck and had to put a Full tank of Tesco 95 Ron in. This tank gave me 390 miles! I hadn't done any longer runs and as far as I'm aware my driving style hasn't changed!
Performance as far as I could tell hadn't changed noticeably.

Doubting the result I put another full tank of 95 Ron in and surprisingly that gave me 385 miles out of the tank.

I then reverted back to 99 Ron and I'm back to 320 miles again.

Anyone else have experience or results like this? I'm as sure as I can be that my driving style has remained the same and I know my journeys are also so I'm at a loss to explain as I thought the premium fuel was supposed to give a better MPG.

Leads me to wonder whether it's worth paying £4 more a tank.

Any thoughts/experiences?

[MczZippy]

I know the 1.8 is set up to use 95 fuel, so possibly 98/99 is confusing the ecu? I know my fabia vrs would run better on 99 but again the Ecu was tuned by vow for 99 fuel

[joe6]

Some of the Golf Mk6 GTI guys have put problems of poor slow running down to 99 fuel (nitro and momentum) but I have not had any problems with mine.

[Penarth Blues]

So,

I've had my GTI for 6 months and covered 4000 miles.

I've run my car on Tesco momentum 99 since new and have always got 320-330 miles from a full tank.

A few weeks ago I was stuck and had to put a Full tank of Tesco 95 Ron in. This tank gave me 390 miles! I hadn't done any longer runs and as far as I'm aware my driving style hasn't changed!
Performance as far as I could tell hadn't changed noticeably.

Doubting the result I put another full tank of 95 Ron in and surprisingly that gave me 385 miles out of the tank.

I then reverted back to 99 Ron and I'm back to 320 miles again.

Anyone else have experience or results like this? I'm as sure as I can be that my driving style has remained the same and I know my journeys are also so I'm at a loss to explain as I thought the premium fuel was supposed to give a better MPG.

Leads me to wonder whether it's worth paying £4 more a tank.

Any thoughts/experiences?

I got what I thought was pre-ignition on first start up when cold from using 99 RON. Not happened since switching back to 95 RON. Managed 45 to 46 MPG on average on a 1000 mile round trip from Cardiff to Edinburgh and back, via the Lake District and Leeds.

[C_Randell_23]

I have done similar back to back tests and posted up here before on another thread. Found no difference between the 2 at all, what makes all the difference to the mpg comparing the two is how many miles I drive with the sport button pressed in, mpg always goes down as i accelerate to hear the grumble and it puts me in a sporty mood.

Personally I would always just go for premium brand fuel like bp 95 as these have more additives that clean the engine, my mate always uses tesco 99 ron and his oil goes blacker a lot quicker than my oil. I like to run a 97/99 ron fuel from premium brand every 3rd or 4th tank to keep any carbon deposits away as these tend to have more detergents in them.

[RUM4MO]

I agree basically about going for "premium" petrol brands, ie petrol from oil companies, but, it is not the base fuel that helps normally, it is the essential additives that turn the base petroleum spirit into something that modern cars need to run efficiently. I would tend to trust the "main players" to use a useful cocktail of additives, remember base petroleum spirit is pooled/shared across UK, so you will be using base spirit from your nearest refinery - but it will have been manufactured to tight tolerances so fit for use.

99 versus 95, I read a bit about this somewhere and found that most of the time, 95 is lifted up to 99 by adding Ethylene and that its specific energy co-efficient is lower than the base 95 spirit, so engine outputs could be lower and MPG could be lower. When you use 99 in an engine that demands it, that makes no difference it only becomes an issue when you use 99 in an engine that has been optimised for using 95 fuel.

My wife used to have a late 2002 Polo with a 1.4 16V 75PS engine, rated for using 95 petrol, due to a problem with it burning oil (oil separator problem), it used to pink heavily so I started using 99 Shell petrol, which sorted that out and it then had reduced MPG, which initially I had not expected, though that engine ran a lot better with 99 petrol, so it does seem to be true!

BP, I would normally sing their praises as they are a "main player" - but it seems like their petrols when tested against other main players, now fall very short - I don't know what they are playing at, probably just buying what is available cheapest and mugging their customers! Luckily this does not affect me as BP is not local to me, I'll stick with Esso and Mobil 1 oils!

Edit:- so maybe the trick is to always buy 95 petrol but one that has the best load of additives - I do agree about the 97/98/99 petrols from main players having the best additives/£ though, so using a tank of that for cleaning purposes still makes sense.

[d7lan]

I tend to mix between 95 and 99 depending where I am (no 99 supply near work unless I take a big detour). And these can be anything from Asda 95 to BP Ultimate or Tesco 99.

Personally, I've never noticed much of a difference in mpg, always getting around 380 miles from brimmed to the red light. The long term average after 6600 miles is up around 44.5 at the moment (but I am aware that the computer over-reads a little).

This may be because my 40 mile commute each way is 37 miles of motorway - if I was running on B-roads I'd imagine it would drop. Do you think subconsciously you may be pushing slightly harder when you know there's 99 in the tank??

Sent from my SM-G920F using Tapatalk

[Fox1429]

I thought it could have been that initially but on the second tank of 95 I consciously made sure I made progress occasionally. And 70 miles extra in each tank was quite a difference (around 20% more).
I've just filled up with 95 again after another 320 mile (range) tank of 99 so will be interesting to see if the next tank improves.

[joe6]

Fifth gear did a fuel test a while ago that looks scientific. The test and results are on this link: https://www.youtube.com/watch?v=WTaBngvsPrc .

I always go for premium brands for the additives so I suppose I am sold by the advertising about cleaner engines. I have generally found less soot around the chrome tailpipe with higher octane fuels - not very scientific proof.

[SRGTD]

I always go for premium brands for the additives so I suppose I am sold by the advertising about cleaner engines. I have generally found less soot around the chrome tailpipe with higher octane fuels - not very scientific proof.

Same for me Joe. I run mine on either Tesco Momentum or Shell V Power, primarily for additives to help keep the engine clean. No carbon/soot build up on my tailpipes either.

[MczZippy]

Is it not cheaper to buy Asda fuel 95 Ron, then add redex (or equivalent) every 5-10k?

At £4 a tank more, I'd spend £2-300 more a year on fuel(4-5 fill ups a month) redex is £5 a bottle...... hmmm very expensive additives!

Terraclean is only £108! You'd only need to do it every 40k for the same effect as vpower

[SRGTD]

Is it not cheaper to buy Asda fuel 95 Ron, then add redex (or equivalent) every 5-10k?

At £4 a tank more, I'd spend £2-300 more a year on fuel(4-5 fill ups a month) redex is £5 a bottle...... hmmm very expensive additives!

Terraclean is only £108! You'd only need to do it every 40k for the same effect as vpower

VW don't approve aftermarket fuel additives. The manual (page 207) states;

'The vehicle should be refuelled with good quality petrol that has already been mixed with the proper additives by the manufacturer'.

'The use of unsuitable petrol additives can cause considerable damage to the engine and catalytic converter. Metallic additives should be avoided at all times. Petrol additives that are intended to improve knock resistance or increase the octane number can also contain metallic additives. Therefore fuel additives sold separately should generally not be used'.

Is it possible for VW to tell if you've used aftermarket fuel additives if fuel has caused engine or cat damage and you make a warranty claim? I don't know, but wouldn't want to give VW any excuse to avoid a legitimate warranty claim.

[RUM4MO]

Well, Terraclean is not much good for modern direct injection petrol engines as the main problem area for these engines that do not have extra manifold injection is, the area just before and at the inlet valves/ports - maybe okay for the very latest with these extra injectors in the manifolds though.

Redex, well maybe years ago using Redex every 6K miles worked, and in my experience, always gave better MPG while running that tank of fuel, but nowadays, I've found Redex to do very little, or at least make any difference while running a tank through the engine - but as to if it cleaned up the combustion areas, I can't say.

[lancslad1985]

Personally, I've used fuel additives in all my cars and not once had an issue (touchwood!). Neither have any of the garages been able to tell. My current Volvo I only use some Redex every now and then to keep the injectors clean as it makes no difference to mpg it seems, but in both my Blue GT and my wifes GTI I've used the Redex Octane Booster and got better MPG than just using the fuel alone.

As someone that works in the car care industry I know people at Redex as I used to work there. Their additives are the same additives used in premium fuel. It's the only way they could get people to buy their products, is to buy the additive packages from the likes of Shell, BP and so forth. Having worked there, the only complaints with Redex in my 4 years were a) People storing it in the car after using it and it leaked and b) people not reading their manual for their ford/bmw/etc and not using the funnel for their easy fuel system, so the redex went all over the floor. There was never a claim regarding invalidating warranty or damaging an engine and they were selling a million bottles a year of the petrol and diesel when I was there.

[gregmkv]

Will test this out in my 6c GTI DSG - usually get around 270-300 miles out of a £47 v-power tank so will fill up with 95 ron next time and report back