[TurboJim]

MMO is the equivalent of a straight weight 5W oil. If you were using 5W-30 oil perhaps you are now down to a combined 5W-25. Since you aren't experiencing problems once the engine is up to normal operating temperature what's the problem? MMO is highly regarded by some on BITOG. Sea Foam not so much.

 

[TurboJim]

Marvel mystery oil is supposed to be used just before your oil change. You want to put it in and run it at idle for a half hour or at low speed just before your oil change. This gets out the gunk. Then put in fresh oil. Marvel mystery oil is a good additive to put 2 oz per 10 gallons in the gas tank to lubricate the fuel system and upper cylinders, so it Lucas.

The amount recommended by MMO for the gas is 4 oz per 10 gallons of gas. Some have found that using more has a negative effect on gas mileage.

Typically if MMO is used in the oil for cleaning purposes it is added 1,000 - 3,000 miles before the oil is to be changed. MMO is not recommended for long oil change intervals. What constitutes a long oil change interval they won't say. From the feedback given on the MMO forum (Ask The Mechanics) it would appear that 3,000 - 5,000 miles is about the limit.

MMO is a very mild cleaner, don't expect it to do much in just a half hour.