I am looking at buying a 1998 420 SEL, but it supposed to run on Premium Fuel only.<br>
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The current owner told me that it is fine to use regular fuel. Is this correct?<br>
Are there any implications of running it on regular fuel only, besides loss of power.(I assume)<br>
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I would appreciate if someone could help me with this.<br>
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Nathanael
If a lower octane fuel is used the engine could ping (knock/pre-detonate) this can permanently harm the engine.<br> If higher octane fuel is available I would use it (you should go further on a tank of premium anyway).
Your owner's manual should provide you with the octane requirement of your engine. The US spec engines were different to the Euro or Aussie specs. While the US machines run happily on 96RON or less, my Aussie spec '82 Euro 280SE with the M110 engine requires 98RON leaded, which of course is now history. (RON=Research Octane Number) Premium Unleaded and Premium LRP here in Australia is only 96RON, and it has detergent additives to help keep the fuel system clean. Our Premium LRPs also have a VSR (Valve Seat Recession) additive to do the job of the lead which was to lubricate the valve seats and upper cylinders. However the good stuff, ie. 98RON fuel is about 8-10cents/litre dearer than the LRP fuels and only 3 companies here market it. (Mobil Synergy 8000, Shell Optimax, and BP Ultimate) Because the 98RON is meant for modern, high-performance cars designed for unleaded fuels, they do not have the VSR additives. Therefore, if your car requires 98RON fuel, you need to add the VSR to the 98RON fuels (not expensive) when you fill up, at least here in Australia anyway. The trade-off with the higher octane fuels is better economy due to the higher energy content. Using the correct fuel means your car will perform like MB intended. The detergency additives of the premium fuels will also help keep your injectors and upper cylinders clean. Check your fuel company's specs and your car's requirements before your fill up. <br> <br> One other thing, if your car is 'detuned' to run on lower octanes, switching to a higher octane fuel will require adjustment to your timing. I don't think any 126 models have 'knock sensors' to regulate the timing automatically. Perhaps someone could enlighten me if this was a feature on later model 126s.
See the previous post. Having said that, your V8 will be quite happy and should not 'ping' with a mid-grade fuel of say 95-96RON. It will of course be happier with 98 or higher :) Choose a brand with detergent additives....they do work.
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