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Saturday, September 17, 2011

AUDI ENGINES Running Regular 87 Octane Fuel

With gas prices so high these days one of the biggest questions I am asked is if an Audi engine is capable of running a lower grade fuel. It is very difficult to see the result of not running the recommended 91 octane fuel over a long period of time because no one typically runs regular fuel through the entire life of their new Audi, especially the first 100k. After many engine tear-downs I have managed to gather a collection of data showing what parts will break down first if a lower grade fuel us used while proving the fact that lower grade fuel will exponentially lower the performance of the engine leading to Lifter/Follower failure, Camshaft lobe wear, Valve seat carbon build up leading to compression loss, Cylinder ring failure and eventually total loss of compression on all cylinders. Typically the cylinders located towards the firewall tend to see the results of low grade fuel first. This is due to the increase of heat both being further away from the cooler antifreeze after leaving the radiator and the heat that is held by the metal of the transmission during longer trips. This heat builds as the engine slowly transfers its energy into the transmission and everything else that it can. The heat of the engine will keep decreasing the time it takes for the engine to prematurely ignite the fuel. You may have noticed if you have ever used regular fuel on a long trip in a car that is built to have a higher octane, after four hours of driving or so it will become sluggish and less responsive than at lower temperatures. 

Destruction is what WILL happen if you run regular fuel often. The reason for this premature wear simply for the fact of using a lower grade fuel is extra resistance on the camshaft(s), pistons, valves and essentially everything that is involved with the ignition process. The difference between PREMIUM fuel and Regular is the rate at which you can compress the petrol before it ignites. Typically well built engines such as the ones Audi produces are a very high compression ratio compared to most coincidentally requiring a more expensive fuel in order to avoid premature detonation during the compression stroke. This is often referred to as knock or ping and will take thousands of miles off the life of your engine. When the fuel prematurely ignites before it is intended too, all of that momentum the engine is carrying is now meeting an intense resistance going in the opposite direction or applying most of the pressure directly on the crankshaft, rod, piston and corresponding bearings. This is the most damaging to the engine because the blunt of the resistance is being forced down at the exact time the rod and crankshaft is at TDC, "when the piston is at the very top of the compression or exhaust stroke." Now all of the pressure is being applied over and over wearing down your engine with every stroke...thousands of times per minute. 

After personally looking at many engines, documenting the results of consistent regular fuel usage and seeing consistently what parts wear first I have came to the conclusion that the cam lobes immediately begin to see the effects of regular fuel within the first 50 gallons. As the cam lobes begin to wear down the intake and exhaust stroke begin to decrease lowering performance. The camshaft lobes then begin to cut through the valve lifter slowly wearing down until the camshaft lobe makes contact with the snap ring in the lifter resulting in a terribly loud TICK. This is usually where most of the vehicles are taken in but in some cases the heat effects the cylinders, rings and valves more than the camshaft and lifters. Either way it is my recommendation that you run at least at 91 or greater octane rating to eliminate any chances of premature detonation and giving your Audi engine the long life it deserves. If you have any questions or comments please feel free to let me know! 


  1. I would have to say we see lots of engine lights on after Audi and Volkswagen customers use low grade gas.Most of the time modern Audi's engine management will sense the poor grade fuel and back down the timing and lower the power.I tell Audi and Volkswagen customers pay a little more at the pump and save a lot in the long term.

  2. Nice information about car parts and it's suppliers.Thanks for sharing it. Engine Mounting | PCV Valve.