Is 10 to 1 High Compression? Or, is it just average these days?


Asked by Jan 22, 2016 at 11:21 PM about the 2010 Subaru Outback 2.5i Limited

Question type: General

Many engines today are higher compression than years ago,  but,  what is really
high compression?    I've read that 12 to 1 or higher engines don't last as long
as those with 10 to 1 or lower?    Is that true?

5 Answers


Not necessarily, usually higher compression engines demand higher maintence but I have seen them last just as long as lower compression engines, it is the RPM's that kill high compression engines, people just can't keep their foot out of them and next thing you know you at or past redline and boom that is all she wrote. When you start getting past 12 to 1 ratios then you need to change fuels, convential gasoline is no longer a good product to run. Then you can get into Alkahol fuels, CNG, propane, methane, or even higher compression engines but slower turning engines like diesels, but that can take us way away from on highway equipment real fast.


1. Diesel. 2. No.


Thanks, so, 10 to 1 compression is average by today's standards?


There are no standards. Are your tires tall?


No, compression ratios can run all over the place, they can go down to 7 to 1 for turbo or supercharged engines, i have seen some experimental engines with ratios down to 6.8 to 1, then they swing back up to 12 to 1 for high horse power normally aspirated engines. if there was a standard it would run around 8 to 8.5 to 1.

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