After replacing my intake manifold gasket, I noticed a good deal of sludge in the engine. From 1 - 10, I would say the sludge situation was about a 6.

My 96 Blazer has 294 k on it. I ran a bottle of Auto RX with a fresh oil change of castro gtx.

My question is, would it be harmful to leave the Auto RX in a really old engine for the recommended 2500 miles during the cleaning phase? Someone told me to change the oil after 200 miles due to the sludge that could be circulating after the clean to prevent damage to the rings. Of course, I really want to get my moneys worth from the Auto RX and dont want to drain it before its done its job, but I don't want to damage the engine either. Any help appreciated, Thanks.

 

Just follow the cleaning program as outlined by Auto-Rx and you'll be fine.

 

My opinion is not to use that stuff look at it this way with the mileage you have on the vehicle it is like a 90 year old man now if the doctors discover a miracle drug that would clear his artires in a month time as soon as the cholesterol broke up in his artires it would send a clot to his heart and stop it. The same is true with your high mileage engine quit using that stuff change the oil and say a prayer every time it gets you from a to b