Why aren't we all using Premuim 98

[Phantom Menace]

All,

I reckon that I will be doing about 5000 miles this summer in Mary-Beth. I hope to get 20mpg on average for these miles. Now if my math’s are correct that makes 250 gallons used. With a conversion rate of 4.544 to litres I make that 1,136 litres. I believe that on average premium 98 octane fuel costs 6p more. I make this £68.16 more if I use premium 98.

This seems small in comparison to the other costs of a caterham and the already discussed in other threads advantages of higher octane fuel so why isn’[t everybody doing this. I only have a 1.6 SS SL but still surely the advantages are greater than cost.

 

cheers

 

is 20 mpg unreasonable for road only blatting

[Graham Sewell]

I agree - except in my case, the genuine leaded 4* is about £1.05 and hence a 30p premium (thanks Mr Brown)...

 

 

Low tech luddite - xflow and proud!

[V7 SLR]

Sorry, but what advantages have you read about using super over normal unleaded?

[Simos]

Depends on your engine V7, you might have to. Not a prob for your K but an issue for my BD timing wise.

 

For day to day driving there's probably little difference but when blatting or tracking the higher octane will give less chance of premature detonation while all other things remain equal.

 

You pays your money and takes your chpice.

 

Cheers, Simon. LRP drinker.

[danwhiley]

What sort of "heart" does Mary-Beth have? Katie is a 1.6K roadsport (2002 Academy) and does an average of 25mpg road-blatting, nearer 30mpg on a long (boooooring) motorway run at about 70mph. Not quite the 38mpg that Caterham claim in their literature, though...

 

Dan.

[V7 SLR]

I think you misunderstood my question. I know just what octane does, and why you should use one variant of fuel over another, but this chap has a 1.6SL which doesn't really need super, yet he says he has read about some "advantages" in using super. If he's a regular thrasher, then he might want to pour it into his car so as to generate peace of mind, but it might still be unnecessary.

 

I think 20mpg from a 1.6 K is pretty poor. My 200+bhp SLR returns at least 26mpg when driven hard on the road, although I drops rediculously when on track, but I suspect that's because I spend more time in lower gears.

[PeterS]

Coming back from the 'Ring, in convoy with other Sevens, doing steady indicated 80 to 85 mph, I achieved 40 mpg with a 1.6 Supersport K. Filled up in Belgium, and drove across top corner of France to the Chunnel, then up from Folkestone to Rugby, all on one tank full.

Suspect that you could achieve better than 20 mpg overall. Don't think the 98 would significantly affect consumption figures.

[Simos]

Hi V7,

likewise confusion, I was writing generically (hence BD comment) and not specifically at the 1.6SS. I also confess to not knowing what the engine is in a 1.6SS but guess it's a K in which case I agree 98 will do little good except on a trackday thrash. (I did also suspect that you knew about Octane :-))

 

I'd love to get 20+ mpg from my beastie but then I ain't got a K + ECU.

 

Simon.

[Phantom Menace]

Cheers guys. Mary-Beth is my weekend fun and as such will rarely do anything but blat on the roads. She is unlikely to do more than a couple of trackdays a year but will not venture on the m-way much either. Her heart is a 1.6 k series supersport and I suspect will see 4-7 thousand rpm most of the time.

[Simos]

Phantom menace...? Isn't that the red/black guy with the horns...? Don't you get wind noise and buffeting at speed ?

[Bob Corb]

K series engines on Rover Mems ECU's cant detect the change in fuel quality so they wont take advantage of the reduced propensity for detonation, so no more power.

 

I filled my tank with Optimax the other day. Doesn't appear to make any difference.

 

If you were mapping the engine on a dyno and used 98Ron for mapping then you would make more torque compared to an engine on 95Ron if it was det limited at a particular speed (usually at low engine speed). Max power still isn't affected unless you have a mental compression ratio/full race engine/highly turbocharged engine.

 

BC

[Hibster.]

Bob

 

Thanks for the factette on the MEMS not being able to tell & therefore benefit from the rating of the fuel.

 

I'm sure I'd been working on the idea (perhaps from what a Caterham sales person told me mad.gif ) that the 1.6 SS engine produced 140bhp on Super and 138 on standard UL, not much of an increase but perhaps on a par with the what an upgrader might expect to see from a heavy part (fibre glass) to a lighter one (carbon).

 

Not that this is really of an issue to me in that my car has run on little but Tesco UL for most of it's life although Eddie H did manage to lose me on a Blat back from the Goat last weekend blush.gif

 

Paul

[DohNut]

I would be inclined to spend some of that 60 pounds on tesco petrol and a dose of Redex.

N

[markb905]

I have for some time put Optimax in my VVC and thought it did make a difference, couldn't get it over the weekend and ended up with UL again, couldn't tell the difference!!!, I thought the optimax did make a difference to the car under load but i think it's difficult to tell, has anyone done any real back to back test (other than Shell that is)

 

Mark

 

Edited by - markb905 on 12 Apr 2002 22:23:14

[F355GTS]

BMW 540, +8% fuel economy and much better pickup...substantial improvement

Ferrari 355, no noticable difference compared to Super UL

Caterham, too new to know but somebody posted that you need to do two or three tankfuls before you see the difference

 

Mark

[Bob Corb]

I agree that the BMW would see some sort of change as I know their engine management systems quite well. Unfortunately Rover (under BMW) didnt benefit from the Bosch technology they had.

 

The K would make good use of it, it does appear to be quite spark sensitive. Perhaps in future with further tightening emmisions regs MG Rover will adopt a more advanced EMS and then fuel quality effects will become significant.

 

As to a 2BHP change from using 95 to 98RON fuel I'm unsure. A 2 BHP variation is within the test to test variation I would expect to see on a dyno. It would take a lot more than this to have a detectable effect. A figure of 7BHP is banded around generally as being just detectable on the road.

 

The last time I did a back to back to back test (on an NA engine with 80BHP/litre) on a dyno between 95 and 98RON the maximum power figure didn't change significantly.

 

I may try a couple of tanks of Optimax just for curiosities sake. Dunno how I'll measure the difference (certainly not Vmax!!)

 

BC

[V7 SLR]

I seriously doubt anyone can tell the difference in petrol when driving their car. The calorific value (read: energy content) of Super vs Normal is the same. The burn rates are the same (once ignited). The only difference is in their ability to resist detonation. Tell me how that can increase your power..???

 

OK, I'll tell you. You have to rev your car harder, past the point where Normal UL would have started to self detonate, or you have to design your engine with a higher compression, or run it hotter. All of these factors try to make fuel self detonate. By using Super all you are doing is allowing yourself the luxury of being able to rev harder or design your engine better.

 

As for increasing fuel economy... how on earth can THAT be possible? Your ECU still dumps the same amount of fuel into the engine, UNLESS it knows you are using 98 over 95, in which case it may alter the ignition timing to suit the better fuel. Not really a fair comparison. On a Se7en, there isn't an ECU around that detects knock (thats how they all detect what fuel's in there) so there isn't that "unfairness". A Se7en will use the same amount of 98 as it uses 95.

[Tight fart]

my fireblade runs better on 98, on 95 it hesitates from part throttle. I was going to dynojet it but optimax seems to cure it.

 

T.F@O.F