If i switch my car's engine oil to synthetic oil,do i have to flush the block with a cleaner before switching?

that dpends on how often u have change dthe oil to this point and how many miles are on the car.. if it mis new and u have changed the oil regularly, u just change it. if u r lazy or tried to get as many miles as possible out of every oil change, then flush it as follows... drain old oil, and add 75 % cheap 30 wt oil and i can of engine flush. and rune at an idle for 30 minutes. DO NOT DRIVE!!!!!! drain and add 4 quarts of 10w30 oil and idle for 30 minutes, to clean out the cleaner. thsi is the final rinse. then add synthetic. u should be fine after this. just don't neglect ur oil, do not assume u don't have to check it or change the filter either. and do not race it at all. synthetics are for grandma style drivers.If i switch my car's engine oil to synthetic oil,do i have to flush the block with a cleaner before switching?
no,you don't have to flush it,synthetic oil will blend with any oil made,all you do is change the oil like you doing a regular oil change and that's is,switching to synthetic oil is one of the best things you can ever do do for your car,it will make the engine last a lot longer in it,and id does help with the running of it as well as help improve the mileage also,good luck with it,hope this helps.If i switch my car's engine oil to synthetic oil,do i have to flush the block with a cleaner before switching?
No, no flush necessary. A good synthetic will actually start washing away sludge build up. Rarely it is possible for some chunks of sludge to get loose in a flush and move around until it cloggs an (other wise good) oil passage.





Synthetic oil is fully compatible with conventional oil. Jennifer S (above) wrote that you cannot not go back. I'm sure she mean well. But that's some crap that some quicky lube and no-good mechanic tells people so you would be tied into spending more money.





It is a good thing that you should always stay with synthetic. But in a pinch you can go back and forth any time you want.





You can even get synthetic BLEND, which is a mixture of synthetic and conventional oil. I mention it here so you understand that they are compatible, but I do not recommend it. The whole point of synthetic is getting the highest ';purity'; of desired oil. Then mixing it with ';impure'; oil is stupid. Just imagine going and getting purified water and then mixing with faucet water. Now you DON'T have purified water.
no dont flush it....syn is 100% able to mix with regular oil...
If the car is old or is high mileage I would not do it. other wise no you will not need to flush it . you might change the oil sooner on the next oil change. but the most important thing ,stay with one type of oil and one brand of oil.
We've recently switched our cars to synthetic oil because of the high mileage. I'm pretty sure you don't have to, but I do know that if you start using a fully synthetic oil you cannot go back to non-synthetic.