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Why Not To Use E85 In Your AMG

July 24, 2023

Blown C63 507 Motor

In our everyday adventures of being European mechanics, we tend to come across quite a few different types of damage to European cars. After all, we are not just about scheduled log book servicing.

Our auto repairs vary from day to day from Mercedes servicing to brake repairs, exhaust repairs, electrical repairs AAAAAND to the odd MAAAAAJOR disaster like this poor guy here who owns this C63.

May we add, it is also a 507 Edition Mercedes.

We carry out major works on all AMG variants but this is one of the big ones. This vehicle was brought to us initially from the get-go when the client purchased it back in 2019.

From time to time it would throw an engine light. Usually being a sensor, a malfunctioning coil pack, a broken plug and another sensor.

It also activated engine lights on two separate occasions to do with fuel injectors failing.
A little unusual for a vehicle with at the time less than 60,000 KLMS on the clock as AMG’S are normally reliable cars. This one was proving other than reliable which we found strange. This vehicle also belongs to our SEO Pro at PK SEO who also takes care of our SEO

Our SEO guys loves his fast cars so like all our customers, we always do our best keep our SEO guy happy.

We do not like to see our customers unhappy so we really go out of our way to fix everything that needs to be fixed and get our clients cars back on the road. With this 507 though, the break downs were just unusually common.

 Every time something went wrong it always usually led to blocked injectors or partially blocked injectors. On the last injector blockage, we decided to carry out further checks to get to the bottom of these issues as the engine was also intermittently blowing some smoke form time to time.

Fuel System Check And Inspection

When it comes to engines constantantky breaking down and activating engine lights, it eventually alerts you to the fact that there is something usually more sinister going on. Engines don’t consistantky blow O2 exhaust sensors or crack spark plugs, especially when the vehicle in question is driven by a mature driver and owner. This car is never driven hard so it beggars belief it could consistently break down or auto parts or engine parts fail on a regular basis. We knew something was going on and we know that higher than regular cylinder temperatures will cause system part failures.

What got our attention was the first sign of a blocked injector. Injectors don’t normally block up on these cars as they carry very fine fuel filtering systems designed to stop anything other than fuel reaching the injector so a blocked injector is a little unusual.

A partially blocked injector will cause a cylinder to run leaner therefore increasing cylinder temps which in turn cause premature failure of engine components.

Seeing it was only the first time, it did get our attention but it also brought the fuel system into question. When the second injector blockages occurred, we then decided to further investigate and dig deeper into the fuel system so we disconnected the fuel line to the rail to pull out some fuel. Upon pulling the fuel line off the rail, it immediately appeared before us that a corroded fuel line is not normal for any vehicle let alone a 507 Edition AMG.

Draining The Fuel

Contaminated Fuel

We have come across quite a few cars with contaminated fuel but nine more so than this. There were extremely high levels of rust in this fuel which called for a full fuel system drain including draining the fuel tank and inspecting the pumps and filters.

After discovering the fact that we had a corroded line, we thought it was a good idea and dig deeper into the fuel system.

It is often a case of going deeper into the rabbit hole when you are trying to identify or find the root cause of an ongoing issue.

As stated, these cars do not usually pose problems like this and we knew we were looking at something more and when the we disconnected the fuel line and found a corroded fuel line, we knew this car was in trouble so we thought we would drain more fuel from the fuel tank.

After havinf rained all the fuel from the tank and dicovering such high levels of contaminated fuel from rust, we discpovered the fuel pumps were actually highly corroded, fuel filters sevely blocked as well. It was incredible how thjis C63 Mercedes still actually ran.

Finding heavily corroded fuel pumps is not a normal sight within a fuel tank and seeing rust within fuel raisl is also not normal.

Realistically speaking, rust within the fuel system should not find its way to thye engine and potentially block fuel injectors. This is highlky unlikely give the fuel system filetrs these cars run. After all, they do run twin fuel pumps with twin filetrs.

Finding corriode dlines with corrode fuel pumps suggests that this is more than just a case of bad fuel within the system. This vehicle did not just run one or two bad tanks of fuel as fuel pimps rust iobver time. Not just with a fuew tank fills.

Enter The World Of E85

If there is one thing that is really unique about this car compared to any other C63 we have heard is the exhaust system.

This car rumbles the entire workshop when it starts and that was inevitably one of the deciding factors that enticed this customer into buying this vehicle.

Having an exhaust on this vehicle was also a giveaway that something may have been done to the vehicle prior to the owner purchasing it.

Enter the world of E85. Corroded lines, heavy amounts of rust sitting in a fuel tank, corroded fuel rails, rusted fuel pumps, partially blocked injectors, o2 sensors failing from higher cylinder temps due to partially blocked injectors only leads to one thing. E85 fuel had been run in this car for an unknown period of time.

The one tell tale sign was the engine every now and then would blow smoke but this was ever so intermittent. This was a sign of an impoending engine failure. It was just a question of time.

Obviously the previous owner who owned this car ran it on E85 unbeknowst to him that these vehciles are not designed to run on corn syrup and was obviously unaware of the fact that this would over time lead to loing term damage.

Obviously it would have been noticed from the intermittent plumes of smoke that some level of engine damage was caused and therefore disposed of the vehicle before any major engine failure. Lucky for our customer, this vehicle was under long term warranty.

The previous owner obvious;y had the car tuned by a poor quality tuner who pushed this engine to its limits which realistically speaking, no engine is ever tuned from the factory to run on the limit of its tune.

Safety parameters are always put in place to protect all moving parts within engines or gearboxes. May owners of these cars fail to realise that these vehicles are already performance tuned form the factory.
After all, it is why they cost the money they cost. Purely for that reason of reliable performance

This engine either died from detonation or the slow degradation of a dying fuel system which was starting to block fuel injectors which can also lead to detonation over time which if unattended. This then eventually leads to engine failure.

The beautiful thing about the C63 is that it is a mighty tough engine and can take a walloping in punishment but can it take E85 and run on an otherwise different tune and stay reliable ? No it can’t.

The one noticeable feature of this engine is that it performed till the day it just started missing from broken ring failure.

There was no slow decrease in power over time. This motor just suddenly stopped performing through a very noticeable misfire and upon carrying leakage tests and compression tests, we discovered one cylinder down completely and another on the way out

So, have you been thinking about running your car on E85? Well if you have or currently are running on E85, expect the same over time to happen to your own vehicle If the vehicle is not designed for E85. it is our best advice not to alter the tune of your engine.

The engines in German performance saloons are designed to perform with total balance to the vehicles capability and to do this reliably every day. The min ute you change the tune of your engine, you upset this balance.
There is nothing we can not undertake and there is nothing we can not obvercome. Even bad fuel system damage like this and replavceing broken engines.

This engine however died an early death because the previous owner was unaware and killed an otherwise perfectly balanced performance car. Our best advice ? Run the fuel in your car that it is meant to run on and you will not encounter these problems.

We hope you enjoyed this post and of you have any question don’t hesiate to call us