Originally Posted by missouriguy1973
10.3:1 is pretty high compression...
Most cars around or above 10.0:1 require 91 octane unless they are de-tuned by removing some timing so they don't detonate...Which is what they probably did with the 2010's...The only reason why the 07-09's could run regular, with lower performance and mileage, is because the knock sensors would kick in to lower the timing...
10.3:1 isn't high at all. I'd consider it low borderline highER
compression or on the higher end of medium compression levels and I have no idea why they would require premium. Most other auto manufacturers that are sub 11.0:1 on a NA engine are running regular For example, all of the following have a higher compression than the Altima and run regular.
10.4:1 - Honda Fit
(since 2003 - maybe 02)
10.5:1 - Toyota Yaris, Honda Accord (both 4cyl & V6 - including crosstour), Honda civic (R18 4cyl),CR-V, odyssey (with VCM), Pilot
10.6:1 - Chevy Malibu
10.8:1 - Honda Civic & Insight Hybrids
10.0:1 - Honda's other V6 offerings are all on regular in the the Odyssey (non VCM) and Ridgeline. even Chevy is at the 10.0 mark for their 4cyl engines.
10.3:1 - Ford is matching the altima's 10.3 on both the 3.0 & 3.5L V6 Fusions & Taurus.
In honda's lineup, only one vehicle has a sub 10 compression ratio (the element) at 9.7:1 - not quite sure why though. The only one that requies premium is the Civic Si at 11.0:1.
My experience as many know is primarily with the Honda side of things and I've never felt any performance or economy increase by running premium in the Fit, our Civic, my Integra GS, prelude, or Ridgeline. The only time I noticed anything was in the Ridgeline. We towed a 2700lb uHaul trailer and used premium; the difference was mainly in what I expected... I only lost 1mpg while towing and I expected at least a 4 or 5mpg loss.