Which Fuel

[grayman]

Having had a diesel Leon for 8 years (and a diesel VW Bora for 4 years before that) I now have a 1.4 TSI FR 150 ACT so back to unleaded for me.

Is it worth using Super (98 RON) rather than Standard (95 RON) in my car from new or is the extra cost not justified? I read somewhere that any performance/efficiency gains would only be noticed in highly tuned cars with larger engines so perhaps it is all a waste of time.

I generally get my fuel from my local Morrisons and despite in the past also using BP or Esso I can't say I noticed any difference between the supermarket offer and the named brands. I can't believe that when a supermarket tanker lorry pulls up at a refinery it will be directed round the back to some 'special' area to be filled up with an inferior product.

This might have been covered before but my search on recent forum threads did not show anything so would be interested in what people thought about the topic with regard to the newer 1.4 petrol engines.

 

[Mr Mustard]

Just filled up with Momentum 99, previously only ever used regular 95. I'll see if there are any improvements over the next couple of weeks (although I believe it takes a couple of tanks to notice a difference).

 

[shadak]

I was researching this when I bought mine. Although its a 1.8T it may be similar.

In the end I got to a technician from Porsche in our country (via Seat central) who said these engines were designed to run on 98 , said I could use 95 fine but all the tech data was measured with 98 and I may not get the same performance/economy using 95. I started with 98 and havent tested 95 yet as Im scared lol.

 

[JMAC]

I had a problems with my TFSI Octavia vRS, particularly cold starting - it would almost seem as if it wasn't going to turn over. It almost coughed until it got up to temp too, again on cold mornings.

I then read something about 95RON causing problems with a magazines S3 longtermer, lower octane fuel was causing a build up of soot deposits in the cylinder heads (?) 98+RON fuels burn more cleanly and should stop this build up. I later confirmed this with my Skoda service dept.

I switched to VPower from then on and didn't notice any further problems. I didn't reach more than 50K in my Octy but I've seen other reports of A4's and TT's having major engine problems at 70-90K. Not sure if that's wholly do with fuel choice or just an inherent 'characteristic' of the 2.0 TFSI engine.

I *think* the TSI engines can also be affected by these build ups. Not sure if there's much or any difference between a 1.4 and a 2.0 though.

If I had one now, I'd spend the extra few quid on filling the tank with 98/99, especially if I planned on keeping it for 3+ years.

 

[surrealjam]

I have ran my 1.4 TSI (albeit the 140ps version) on both 95 and 98 RON petrol - mostly both from Shell. I haven't noticed any difference in performance or fuel economy though perhaps "under the hood" it may...

I think it's a good point made above that if you are planning to change the car at 2 or 3 years old with 40k on the clock, I can't believe using high quality 95 RON or high quality 98 RON will make much difference.

I like to run the car nearly empty and put 98 RON in once in a while - give it some beans and blow out the cobwebs for 400 miles. Plus, it's just good fun, right?!

 

[yellowcone87]

I've used Tesco momentum 99 in mine since new. I can't say whether it results in any gains, since I have nothing to compare it with.

However, I have noticed quite a few people complaining about high oil consumption on their TSI, while mine has used literally none at all in over 10k of mixed driving. Could be coincidence, but at the end of the day the manufacturer recommends you use the best fuel available, so that's what I do. Tbh I can't understand why anyone would spend thousands of pounds on a new car and then skimp on the less than £2 difference in each fill up... Look after it and it will look after you.

 

[P0LKR]

I think the only Mk3 Leon that needs 98/99 is the cupra if you look at the downloadable pdf giving the technical specs.

When I had my Mk2 cupra i ran it on 99 and it made a big difference to performance. I run a 116i BMW at the moment and it prefers 95ron. Its not a performance engine though. Ill be running my new cupra on 99 come May/June.

 

[Seastormer]

Run mine on Asda 95 as all my prevoius Biza Cupra's, tried 99 and no noticeable performance diff over a few fill ups. Also the mpg never changed other than by my right foot, and I kept all mpg/ dist journeys for the tax man as I used to run my own business, so the figs were accurate.

 

[DaFoot]

I'm keeping track of calculated mpg, over diff modes and fuels.

So far I've been using standard Shell (I don't like how much biofuel supermarkets add), but the current tank is Shell Super/Nitro and the next couple of tanks will be.

I'll let you know in a couple of weeks of any difference...

 

[shadak]

It may be a bit different for a diesel .. no ?

 

[Mr Mustard]

I think the only Mk3 Leon that needs 98/99 is the cupra

I'm sure the lesser petrol engines don't need 98/99, but it would be nice to know if they would benifit.

The fuel computer in my car showed 32.8mpg on my last tank (95ron), but checking it brim to brim shows a true 30.9.

 

[yellowcone87]

Well, my 1.2TSI DSG is averaging 47.2mpg (according to the car anyway) over the last 1600 miles, and I'm no slouch. It also does the 0-60 dash faster than the brochure seems to suggest too. Over five attempts on a flat, even road it averaged out at 9.4 secs.

I have no doubts it would be happy enough to run on 95 octane, but I'll stick with the 99 just since it seems to be running so sweetly on it.

 

[MrCh00]

This always interest me because I would like to know too. I did some Google research but there's never seem a positive answer to if it would run any better on 95 or 99. Some say yes some say no.
Anyway since I got the car from new last week I've been filling it up with super unleaded even tho the wife thinks I'm wasting my time and should stick to normal unleaded. Not 100% sure if I will keep the car beyond 3 years as yet.



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[shadak]

I think it depends on the engine, my tank cover (1.8 EA888 gen3) says min.95 and the technicians confirmed the RON98 would be ideal for max performance/milage.

 

[P0LKR]

I think it depends on the engine, my tank cover (1.8 EA888 gen3) says min.95 and the technicians confirmed the RON98 would be ideal for max performance/milage.

I would agree with the technicians. The 1.8 tsi petrol and above will benefit. I wouldn't bother with super on small capacity engines but on the Cupra I think it's necessary to use super so that the power isn't retarded and fuel consumption is optimised.

 

[dw911]

I would agree with the technicians. The 1.8 tsi petrol and above will benefit. I wouldn't bother with super on small capacity engines but on the Cupra I think it's necessary to use super so that the power isn't retarded and fuel consumption is optimised.

I'd pretty much agree with that, no really benefit for smaller engine cars, unless they are designed to use higher octane fuel.

On things like the cupra that are designed from the start to use higher octane, if you then use lower octane fuels, the engine will knock (not good even for a short period) and the engine knock sensors will retarded the ignition timing etc till the knocking(pinking) stops, the ecu will then keep trying to slowly advance the ignition timing trying to get back to its optimum range, of course it can't because the knocking starts again so it retards again and so the cycle continues, till you put the octane in that it's designers/engineers ment for it to use.

 

[Seastormer]

I'd pretty much agree with that, no really benefit for smaller engine cars, unless they are designed to use higher octane fuel.

On things like the cupra that are designed from the start to use higher octane, if you then use lower octane fuels, the engine will knock (not good even for a short period) and the engine knock sensors will retarded the ignition timing etc till the knocking(pinking) stops, the ecu will then keep trying to slowly advance the ignition timing trying to get back to its optimum range, of course it can't because the knocking starts again so it retards again and so the cycle continues, till you put the octane in that it's designers/engineers ment for it to use.

Rubbish, never had any of my Cupra's knocking, ever. It says on the fuel cover 98/95 so both are fine even in a Cupra, and the manual states with a small loss of performance on 95, but you can't feel it.

 

[dw911]

Rubbish, never had any of my Cupra's knocking, ever. It says on the fuel cover 98/95 so both are fine even in a Cupra, and the manual states with a small loss of performance on 95, but you can't feel it.

Not according to bosch and they should know, it's all explained in their technical documents, my explanation was pretty basic compared to theirs but it should give the general idea of what happens when you run lower octane through an engine designed for higher octane

Of course won't hear the knocking, not unless you have a very sensitive microphone strapped to the head, it's not loud like someone hitting a oil drum with a hammer, but it's easily picked up by the sensitive knock sensors on the cylinder head of the engine and the signals sent to the ecu

Rubbish? why do you think your car has knock sensors, certainly not for fun, the knocking is not good for the engine, why do you think they put knock sensors on the engine and gave the ecu the ability to be able to take actions to stop the knocking ?
And if you have the VAG diagnostic system , fill up with lower octane and you can log/view the knock sensors and the signals they send when they pick up knocking, display up on the diagnostic screen

But hey, it's not my engine, run what makes you happy

 

[C_ED_99]

Should be easy to test if someone has a torque app and a Bluetooth OBD dongle.

 

[Seastormer]

Not according to bosch and they should know, it's all explained in their technical documents, my explanation was pretty basic compared to theirs but it should give the general idea of what happens when you run lower octane through an engine designed for higher octane

Of course won't hear the knocking, not unless you have a very sensitive microphone strapped to the head, it's not loud like someone hitting a oil drum with a hammer, but it's easily picked up by the sensitive knock sensors on the cylinder head of the engine and the signals sent to the ecu

Rubbish? why do you think your car has knock sensors, certainly not for fun, the knocking is not good for the engine, why do you think they put knock sensors on the engine and gave the ecu the ability to be able to take actions to stop the knocking ?
And if you have the VAG diagnostic system , fill up with lower octane and you can log/view the knock sensors and the signals they send when they pick up knocking, display up on the diagnostic screen

But hey, it's not my engine, run what makes you happy

Had some of my Cupra's for over 5 years, drove them hard and they ran sweet, no engine probs, maybe that's why SEAT don't say MUST RUN ON 98 on the fuel flap or in the manual, and as they build them I think they know what they are talking about.