Fuel Test Results Update
By Thorney Motorsport
Road car tuning and race car preparation share a lot of common aims. Both are looking to extract as much power out of a given engine as possible, both are looking to extract the best dynamic performance from a chassis for a given purpose, one road, one track, however, the main area of duplicity is the concept of testing.
Thorney Motorsport as a company spends just over 20% of its turnover in testing; new product, new ideas, new lubricants, that’s over £300,000 just on trying new ideas and seeing if they work or not, then refining them for use in either the road or race car development. A little under a year ago we extended this process of testing to fuels, surprisingly no-one (even the fuel companies) had ever conducted open, back to back testing of the main component we all use to extract performance from our road or race cars – the very fuel that makes them go.
The result of that extensive test (the first report can be read HERE) was that the quality of fuel you used in your tank had a direct affect on the actual power output of your car, the difference in power and torque between 95 octane fuel and that tests winner (Tesco 99) was over 10%. Considering people spend thousands of pounds on road car tuning to obtain lesser gains than that and if someone offered us a 10% improvement in power from a race car for nothing more than putting different fuel in the tank we’d take their arm off we thought the information was worth sharing.
Thorney Motorsport are in the business of increasing power for customers cars, there’s nothing magnanimous about our testing of these fuels, from our perspective the better the fuel used by the customer the easier our job is to extract power – we’re not stupid.
The problem (or benefit depending on how you look at it) with testing is that it’s never ending, as soon as you develop one idea another comes along to supersede it, as soon as you recommend one fuel another comes along to beat it so we’ve continued to test and re-test performance fuels as an on going process. Soon after we published our first fuel test report Shell released V Power and then BP released its 102 Octane fuel, as our original testing was conducted on Shells Optimax and BP Ultimate it was only natural that we continue our testing to include these new products.
The Testing Equipment
As before we utilised our state of the art chassis dyno meter – the Dyno Dynamics Low Boy 450 Chassis Dyno. To accurately measure a cars performance you need an accurate vehicle dyno meter (also known as a rolling road) this is a sophisticated piece of equipment that allows you to drive a car as you would on the open road (the wheels turning on rollers) whilst it is strapped in a fixed position, here we are able to accurately measure every output from the car.
Dyno Dynamics are World renowned for creating one of the most accurate dynos available and are used across the globe from everyone from car tuners to fuel suppliers, interestingly it is also the exact same make and model of dyno that BP chose to road show their 102 Octane fuel.
Rolling Road
When cars are driven on the open road they are kept cool by the high volume of air flowing over the vehicle, to replicate this Thorney Motorsport use four one meter diameter fans to generate 120,000cfm (cubic feet per minute) of airflow over the car in our custom designed dyno cell. Two fans are situate behind the vehicle to extract the hot air generated by the vehicle engine and exhaust and two further fans blow air over the vehicle. With all four fans in operation we exchange the entire air contents of the cell every 5 seconds – basically it’s a wind tunnel with a dyno in it. Our dyno is surface mounted to allow airflow under the vehicle (which replicates the road/track) and allows safer strapping of the vehicle to ensure it’s strapped down and not back (which can affect the accuracy of the readings).
On the first test we used three vehicles; a Vauxhall Astra VXR, a Toyota MR2 and a BMW E46 M3 CSL. For the purpose of the extended testing we elected to continue with the BMW as the 6 cylinder S54 engine was the most consistent in the results taking into account ambient and intake air temperature variations. The car was completely standard save for a Milltek Sport exhaust system. The car is also my personal daily drive so an extensive period of fuel measurement could be undertaken.
In the previous testing we conducted we filled the cars three times then tested the fuel, however this time (as we were only running one car) we tested the fuels at regular intervals and regular times of day to ensure near identical ambient conditions and identical engine conditions for accurate comparison. In total (the tests are continuing) the car was run for 11,500 miles with approximately 5,000 of those on Tesco 99, 4,000 on Shell V Power and 2,500 on BP 102. When weather conditions were comparable the car was run on the dyno and the recordings logged. In total the car was run on the dyno over 65 times. The car was tested in ambient temperatures ranging from 6 degrees to 32 degrees with intake temperatures ranging from 11 degrees to 28 degrees.
The Results
CSL Chart, Power at the Flywheel
The red line represents the car run on Shell V Power, the blue line Tesco 99 and the green line BP 102. The difference between Tesco 99 and BP 102 is marginal, the Tesco seemed to perform better at lower rpm with higher power and torque with BP 102 giving slightly higher peak power at high rpm. Surprisingly the Shell V Power under performed throughout the rev range when in direct comparison with the other two fuels.
Torque output for the car mirrored that of power with the BP 102 fuel giving slightly better mid range torque compared to Tesco 99 and quite a lot more than Shell V Power but as the charts show the differences between the three fuels is relatively marginal.
CSL Chart, Power at the Wheels
On the road the differences were equally marginal (and also subjective, ‘feel’ whilst a valuable measure is impossible to accurately quantify) with the Tesco 99 and V Power interchangeable in terms of how the car felt under power, however the Shell fuel did give poorer results in terms of consistency. On a few occasions we felt that the car appeared down on power when running V Power but when tested this proved not to be the case, Tesco 99 on the other hand seemed to feel consistent and we rarely had a time where we ‘felt’ the car was under performing from one batch of fuel to the next. BP 102 was the revelation in the ‘feel’ stakes, when we first put the fuel in the car the BMW certainly felt a lot quicker, in fact we were so convinced it was quicker we tested it straight away (normally we ran three tanks worth before doing any testing) and the result was the green line on the above chart, so whilst the car felt quicker the gains on paper were more marginal. This feel for the 102 fuel was short lived however, on several tests of the BP fuel after it had been in the cars tank for a little over a week we found the fuel significantly dropped power, the car felt flat and power dropped by 3-4% compared to a peak run on ‘fresh’ fuel.
BP 102 Octane Test
All fuels suffer from a process called olefinic breakdown where the relative RON and MON rating drops by the fuels exposure to air, this is why race fuels are always used when completely fresh from the drum as this breakdown can have a dramatic effect on fuel quality. However the process of olefinic breakdown normally takes months in pump fuel so we were surprised at the relative drop in performance of the 102 fuel in such a short time frame.
Another aspect of fuel performance which was more noticeable in this testing was the direct affect of ambient and intake air temperature on the fuels performance. One of the reasons we chose to continue with the CSL in this test was that as a normally aspirated engine there was no turbo charger to affect or be affected by large variances in ambient and intake air temperature. In simple terms all an engine is is a controlled explosion – mix fuel with air then blow it up, the colder the air involved in that process the more oxygen it contains and the more powerful the explosion. This is the reason that some cars (especially turbo charged ones as the turbo charger creates heat) feel a lot quicker in the cold morning run to work than in the drive home in the heat of the afternoon, it's also the reason companies like us spend so much on developing things like charge coolers. With the Tesco 99 and V Power fuels the difference in power from higher ambient and intake temperature runs were in line with expectations; 1.5% drop in power with each 10% increase in intake temperature but with the BP 102 fuel the drop was more dramatic. With each 10% increase in intake temperature power dropped by 3%. This is not to say that the BP fuel didn’t perform in hotter temperatures as the car still felt the quickest when run on the 102 fuel but this performance feel did drop with time in tank and as the temperature rose, at this time we can’t make any formal conclusion on this specific point, needless to say the testing on this point continues.
The General Conclusion
In simple terms, Shell V Power is near identical to the Optimax product that it replaced, in power and ‘feel’ terms it continued to out perform all 95 octane fuels and we’d still recommend owners of all performance cars use the highest quality fuel they can find. However the performance offered by the fuel was sometimes inconsistent.
The Tesco 99 fuel again outperformed V Power in all the tests but the differences between the two fuels were marginal and we doubt most people would tell the difference in their cars on a day to day basis. However the Tesco fuel was the most consistent.
The BP 102 fuel showed the best gains in terms of ‘feel’ and performed better on the dyno and on initial fill up, when the fuel was fresh the power gains were noticeable even above the Tesco 99 fuel. However the gains seemed to dramatically diminish over time or with increases in engine bay temperature a feature which we are continuing to test.
The testing we have conducted deliberately concentrated purely on the performance gains offered by the premium fuels without reference to cost, cost is a financial measure not a performance one. However it would be puerile to simply ignore its reference in testing deigned for the general fuel buying public. In pure cost/performance terms its very hard to beat the Tesco product, on average the Tesco 99 fuel was 5-6% cheaper than the V Power (up to 10% cheaper when compared to some motorway fuel stations). The BP fuel at almost £2.50 a litre was obviously the most expensive and even with our £50,000 per year fuel bill it would be impossible to justify using the fuel with any degree of regularity - £147 to fill the tank of the CSL was even worthy of a picture of the pump price gauge.
Bottom line? Use the Tesco 99 fuel where you can find it, it offers the best, most consistent performance of the fuels available and it’s cheaper than V Power. If you can’t find a Tescos that sells it then go for Shell’s V Power. If you’re feeling really flush, have a point to prove on a rolling road day (days where car enthusiasts compare their cars power on a dyno) or want to extract the maximum potential out of the car on a track day then the BP 102 fuel is worth a go, just bear in mind that £150 a tank would pay for a good proportion of tyres or some decent driver training.
Thorney Motorsport is continuing the fuel testing (we’ve made a rod for our own backs now it seems) so next up on the agenda is a performance test of all the race fuels currently available to see how they compare to the BP 012 fuel which we will undertake on our fleet of Vauxhall VX220 race cars and on our new Corsa VXR road car. We hope to have this next instalment (starting to feel like a soap opera now) at the end of the year. In the meantime we will continue to test the pump fuels and will continue to publish all of our findings.
