X66 - two diesel-based effect and cleaning additives for gasoline and E85

Published 2010 Amended 2021

  I was first doubted whether it is -at all- possible to mix diesel into ethanol or E85? After a few laboratory tests, I found that it is possible to mix diesel in E85 up to 20 per cent (by volume), then it begins to separate itself. It goes very well to mix 15 % diesel in E85, also for E85 of inferior quality (aqueous). Since diesel lowers the octane rating, is a high concentration of diesel in E85 or gasoline directly harmful (for an Otto-engine)! It can therefore only be question of small amounts.

White spirit and lighter fluid has in many cases excellent washing properties and dissolves most contaminants. They are both miscible in ethanol, but can be mixed with ethanol (high concentration) up to 40 volume per cent.

D66 is thus a mixture of 66 % diesel and 33 % white spirit, while T66 consist of 66% hydrogen treated lighter fluid and 33% diesel.

D66 role as the supreme additive for both gasoline and E85 has finally now got competition from T66. D66 still rules when it comes to gasoline - it's about ethanol, one should invest in T66. D66 and T66 have effect-enhancing properties and may reduce the injection time by 25 to 30 %. As an addition, diesel and white spirit solves a variety of organic contaminants in the fuel (for example, PIB*). Diesel has no clear effect peak but it decreases if the dose exceeds 0.5 %. Incidentally shall not T66 over-or under-dosed while D66 has wider margins there.

If D66 alone should be used as a fuel additive so is it preferable to put the right amount of acetone in it, which then needs to be adapted to the fuels gasoline content - this rule can not be applied for T66.

T66 or rather said lighter fluid in the T66 should never be mixed with any type of alcohol or other secondary alcohols. It will be dosed alone and must not come into contact with alcohol until it is united in an alcohol fuel. Petroleum products such as gasoline and diesel, but also acetone are harmless to T66.


* = PIB or polyisobutylene - is classified as a thickening agent, but is still an additive in gasoline and diesel fuels. It has a cleansing effect and reduces the risk of knocking (octane-enhancing). For E85 occur the opposite, it pops out and clogging the fuel system (pink goo). Rhepanol-paste is used in roof assemblies and contains PIB.

    D66          label

Do not store X66 in plastic bottles such as battery water or the like. The plastic softens and shrinks up if exposed to diesel/white spirit for a long time. Instead use a bottle that has contained lighting fluid.

It should be noted that diesel and naphthas feels slippery when you get it on your fingers, so it may well mean that the X66 has a lubricating properties - in addition to the cleansing and effect-enhancing properties.

For cars with electronic fuel injection, it is known since long time back that diesel works as a cleaner, instead of injector cleaning like STP or similar products - but kerosene will also work. I used often diesel myself at the time when there was only petrol available (for a petrol car with fuel injection).

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