Hydraulic lifters hates additives if I must say from personal experiences. The problem is not with synthetic oil or not. If the engine is heavily sludged, the lifters would be affected.

If the oil level is low, high speed driving would have a problem with oil pressure as there is insufficient oil for the pump to work. Likewise if the engine is heavily sludged, the stariner would be partially cloggged and this would result in oil flow problem whereby the pump is not able to work fast enough to provide sufficient oil for lubrication.

Since the oil pan is cracked, you need to either repair or replace it. While ther, check the oil strainer for blockages.

Answered by KHLow2008 (expert)
40,332 answers provided

Thanks KHLow2008, when i had the oil changed i believe they put in 4 quarts instead of the required 3.2 quarts. Could this cause the engine to be heavily sludged (even though i just changed the oil) and yes, i will have to check the oil strainer. thanks & GB

Response from bluebeach1
1 question asked

No, sludge is caused by long term use with far and few oil changes in between and addition of additives.

A little excess of oil does not cause the problem.

Answered by KHLow2008 (expert)
40,332 answers provided