Dave The Hippo

So apparently, before I got my 2002 Mercedes E430, my parents have been putting 89 octane instead of 91. (From ~70K to 131K miles). What issues might be coming along with this error/ what type of wear would this have caused?

kajtek1

The car has knock sensor who will retard the ignition for such occasions.
Potential pinging might affect piston rings and bearings, but if you don't hear any ill effects now, it should be safe.
Check the engine for blowby.

fabbrisd1

Frankly - congrats on your E430. That has been doing fine on 89 - a bit lower fuel economy.

A 2002 at 131K miles - a few items for your consideration from back to front:

1. Dose gas tank at next fill up with 1/2 $9 bottle of Stabil Marine Formula (Blue Bottle) to start injection system and fuel tank sensor cleanup

2. Consider replacement fuel filter - Mann/Mahle/Bosch/MB only - $35 to $50 and you will need 4 replacement fuel line clamps to replace the MB trickster clamps

3. Consider a replacement MAF - genuine Bosch only from a reputable internet seller - about $140

4. Consider fresh sets of spark plugs - OE Bosch 12/$65 - and best to have "boot removal tool" $18 and "swivel thin wall socket" $26 some dielectric grease to dab when reconnecting spark plug harness to the sparkplugs

5, Fresh coolant (MB or Zerex G-05) - if concentrate use only distilled water for the mix

6. Check belt tensioner - belt - idler pulley & fore replacement best to buy Contitech "belt drive component kit for $150 - do not use China made replacement belt tensioner

7. Replace tranny adapter plug $14 genuine MB/MOPAR only - check for internal leakage at replacement. If internal leakage pull/flood-clean Transmission Control module with $8 can of MAF Cleaner - air dry before reinstalling TCM board

8. Consider fresh tranny service w/correct MB approved fluid only

9. Make sure you have Radio Code

That's a quickie list - congrats

8. If headlights are "frosting" - hit Walmart Auto for a headlight cleaning both lenses about $35-$40

Dave The Hippo

Honestly this car really needed an overhaul. Over the past 70K miles, the only thing done to it was oil changes, so it needed a fair amount of maintenance work. In one way or another, I had to replace the fuel filter, plugs, plug wires, TPS, coolant, engine + cabin air filter, as well as rear brakes and all four tires need to be replaced by wintertime. Definitely needs a new battery (more than seven years old and it was struggling the last couple cold weeks of winter) but it rides and picks up like never before with awesome fuel economy.

tjts1

The naturally aspirated M112/M113 is designed to operate it's entire life on the lowest octane fuel available in the US including 87 aki. MB is well aware of the fact that as soon as these cars move on to their second and third owner most will see a steady diet of 87 aki gasoline. The reason your owners manual says 91+ is because the engine was federalized on 91 octane fuel. That's how they got their fuel economy and peak power numbers. It would be illegal for MB to recomend anything else. These cars are sold all over the world including places where 91aki (95ron) is not available. You will not damage this engine by using low octane.

C280 Sport

Now that you have it you can run the correct fuel. Premium unleaded. You will notice the difference...

C280 Sport

Oh good God... 70,000 Miles and they only changed the oil?

kajtek1

" such a good car and still require oil changes?"