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      08-26-2013, 12:50 PM   #75
W///
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Drives: F82GTS, E36/E92M3, Z4M
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Quote:
Originally Posted by regular guy View Post
Let's assume you want to replace the rod bearings every 50,000 miles and calculate the long term costs to 300,000 miles based on that. You end up spending $2,400 for each bearing replacement (labor included) at 50k, 100k, 150k, 200k, 250k, and 300k. You've spent $14,400 going this approach and gets you to 350,000 miles.

Now look at the cost to do remove the motor and have the crank machined starting at 50,000 miles. If you go this route, the motor could/should last another 300,000 miles. The cost for this approach will be approximately $5,500 if you don't rebuild the entire engine at the same time and about $10,500 if you do (includes new pistons, etc.). I think most people will opt for the $5200 route, which is just above the cost of two bearing replacements without resizing the crank. This approach also gets you to 350k miles.

I realize that some people may choose 80k miles for change intervals, and it may cost less than $2400 each time (depending on the shop). I also realize some may not see 300k miles out of their engines. Whatever change intervals, total miles, and prices you feel comfortable choosing, just plug them in and see if it's more cost effective for you to have the crank reworked instead.
For me, it's definitely switching the bearings out, rather than pulling the crank out. It'll take me a while to put 50k miles on the car.

I know running oil thinner oil is only a band-aid, but who knows, maybe that can really extend the life of the bearings?
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