Fuel System Cleaners - Why Wait Until Tank Is Nearly Empty To Use?

[bcwang]

Strange, stp products used to say pour into nearly empty tank and fill up. Now, the products say to pour into a full gas tank. Anyone know why they changed their instructions?

 

[Ken2]

Don't most (all?) modern fuel injected engines have a fuel return line back to the tank? That will soon mix everything inside the tank.


Ken

 

[brianl703]

A lot of newer vehicles have a returnless fuel system. Well, let me rephrase that...all of the newer Ford vehicles have a returnless fuel system.

Prior to that, fuel injected systems did indeed have a return to the gastank.

 

[T-Keith]

quote:

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Originally posted by brianl703:
A lot of newer vehicles have a returnless fuel system. Well, let me rephrase that...all of the newer Ford vehicles have a returnless fuel system.

Prior to that, fuel injected systems did indeed have a return to the gastank.

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True to some extend. Most newer GM, Dodge, and Ford cars have "returnless" fuel systems. They really aren't that different, they still have a fuel pressure regulator that sends excess fuel back to the tank, however they now mount it in the tank instead of on the engine.

So the mixing effect will still be there.

-T

 

[TallPaul]

quote:

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Originally posted by bcwang:
Strange, stp products used to say pour into nearly empty tank and fill up. Now, the products say to pour into a full gas tank. Anyone know why they changed their instructions?

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I'd assume they got complaints of rough running from people who poured it and forgot to fill up right away.