Optimax? Ever heard of it? It’s the stuff that Shuey recommends for your car in the adverts on TV. But what is it? 

Optimax is a new petrol developed by Shell and it’s widely available in the UK (Except Scotland). We often talk about the best exhaust or oil for our car, but have you ever considered what is the best petrol?

Well, Shell did, let me explain. There are three types of petrol commonly available at the pumps and these all have different Octane ratings. Octane measured in ‘RON’ is basically a measure of the quality of the fuel. The higher the octane rating the more ignition advance you can run before detonation occurs. So the higher the octane rating, the more power your car will produce. The three fuel types available are; Premium Unleaded, LRP (Lead Replacement Petrol) and Super Unleaded. So what’s the difference?

Premium Unleaded has an octane rating of 95 RON, LRP varies a little and can be between 95-97 RON. Super Unleaded is rated at 97 RON. Optimax which Shell claims increases the performance of your car and has been specially developed for ‘performance cars’ has an octane rating of 98.6 RON.

In Japan higher quality fuel is available with an octane rating of 100 RON (like our old ‘5-Star’). This is great for Japan but we can no longer obtain 5-Star, so Optimax is the next best thing.

But at what price I hear you say? Well Super Unleaded (SU) has always been a little more expensive as it is sold as a ‘premium fuel’ and in this respect Optimax is no different. As it is a low-sulphur based petrol Optimax is normally priced slightly lower than SU.

Now to the important part. Does it work? Well I run a highly modified supercharger that last time on the rolling road produced 182Bhp (static) running on Optimax. When I put the car on the rollers again on BP Super Unleaded it produced 178Bhp. That’s a 4Bhp difference! Adding a performance exhaust like a Magnex/Mongoose is unlikely to net you much more than that!

Of course you don’t have to take my word for it. EVO Magazine recently tested Optimax on 3 of their fleet cars (Civic Type-R, Jaguar XJR, BMW M-Coupe). Shell claims that Optimax ‘cleans’ the inlet valves of the engine and that heavy constituents in other fuels can leave deposits on the backs of the inlet valves with the poorest quality fuels leaving the most which can lead to a tar like gunge within a 1000miles (EVO, 2002). 

In order to form an objective test as possible EVO placed cameras into the inlet tracts to determine if any deposits were present. Their test was to run the cars on ‘other’ unleaded fuels for 1500 miles and then use exclusively Optimax for a further 1500 miles before taking further pictures of the inlet valves. EVO also recorded the cars’ in-gear performance figures before and after the test. 

Interestingly when EVO took the initial inlet valve pictures the Civic had the most deposits. This car had been using cheap supermarket petrol (so take heed!). The BMW and Jaguar were relatively clean using a variety of SU and regular unleaded.

So on to the results! The inlet valve pictures showed a marked improvement especially on the Civic whose inlet valves were rid of deposits entirely. The other two cars had very clean valves before the test so results were less marked. For the performance figures the best results were again on the Civic with a loss of 1.19 seconds for 60-80mph in fifth. The drivers of the cars all reported smoother running and a more responsive engine. EVO’s verdict? Shell’s Optimax does what it says it does, leading to smoother running, increasing performance and preventing build-up of performance-sapping deposits.

I would have to agree with EVO as I do try and use Optimax wherever possible and would refuse to use anything else when I go to the track (I even take a 20l Jerry Can full of the stuff!). I have never used anything less than SU but do notice that my car too is smoother and delivers better performance with Optimax. EVO’s other suggestion that ‘You get what you pay for’ seems to ring true here. Just as cheap tyres (you’d be amazed at the difference between cheap and premium tyres in terms of roadholding, predictability and handling. But that’s another article!).

Incidentally to get the most from Optimax you may need to advance your ignition timing. This is best achieved on a rolling road where everything can be monitored though you may be able to achieve the same by trial and error though be careful that the engine isn’t ‘pinking’ under load. I have distributor-less ignition so mine automatically adjusts. Re-setting the ECU may also help. 

Something I haven’t mentioned is ‘Octane Boosters’ most commonly found in the drag racing scene. These are available from most accessory shops and some can raise your octane rating by as much as 7 points. These are no doubt effective but can be expensive if you are to use them long-term. 

Try it, you’ll be surprised!

Lauren

Trackday Queen