Civic VX Lean Burn Questions

[Wandering Albatross]

I recently purchased a 1995 Civic VX with 120K miles on it. The car is a diamond in the rough and is 100% stock. So far I really like it and the FE has been respectable.

My first tank driving roughly 65mph on the freeway resulted in 43mpg with the correction for 175/70/13 tire size. From what I gather my FE could be better.

The previous owner had 175 size tires on the car at roughly 30psi and used 10-40W conventional oil. The tires were recently replaced with Sumitumo HTR T4 LRR tires at 50PSI at the OEM size. The ride and traction aren't too bad despite the high tire pressure. The spark plugs were replaced with the proper NGK V-power. Additionally, I'm planning to change the engine oil to synthetic 5-20W. Overall, the engine runs very well.

The clutch is getting replaced in the near future and the gearbox will be synthetic as well. I realize that the tires still need to break in, but I suspect this tank will be better than the last tank despite more city driving. I'm still getting used to the tall gear ratios as well.

I'm hoping to break 50MPG on a regular basis with mixed driving. The catch is that I have a California VX and from what I gather I'm losing roughly 4MPG. I suspect the CA VX does not run as lean in order to produce less NOx. I currently have a four-wire O2 sensor and would need to chase down a five-wire O2 as well as a 49-state ECU.

Is that all that I would need to change? If anyone has personal experience converting to the 49-state version I'd love to hear from you.

Have people had good success with monitoring their lean burn mode? I know it is easy to set something up with a multimeter, but I'm wondering how much it actually helps MPG-wise if you can watch when the car steps out of learn burn mode. Watching the number changed is one thing, but can you get results?

I'd to be interested to hear any other means of obtaining better mileage without significant effort and/or mods. At this point a boat-tail, pulse and glide, driving at a max of 40MPH, etc. would be difficult. I do glide down longer hills in neutral.

I look forward to hearing everyone's replies. I know there are a number of experienced VX owners on the forum!

Thanks!!