Project: 1997 Honda Civic HX

[ps2fixer]

I'm not sure how honda engines handle hills vs mpg, but mine REALLY drops when going up a hill, something along the lines from 50-55mpg down to 33mpg for an overpass if I try to maintain about the same speed.

If you don't have a scanguage, or some other gauge, get one! From my understanding, for a large hill you will want to load the engine to 80% load which is about the most efficient load you can put on a gas engine. I would play with different methods to find the best one for that hill using a scangauge. If it isn't overly huge, let the car slow down and DWL (drive with load) up the hill. I would assume unless the hill is rather steep, speeding up before the hill is eating more gas than what it is saving you. Go slower up the hill, and faster down the hill (best to EOC if that is an option for you and the hill meets the requirements ex: steep enough).

[brucepick]

Welcome to the finicky but rewarding world of HX!

For your after work commute, check engine coolant temp (ECT). With a "stock" tstat mine settled in at 182 deg F after just a few minutes or miles on highway. On local roads with lots of EOC, I've covered 6-8 miles and still not get above 160-ish. If yours doesn't warm up promptly that would hurt you.

I like the 195 deg I get now. Install a partial grill block and pay attention to ECT. Recently I switched to a 180 deg tstat which gives an ECT around 195 deg F, IF there's an appropriate grill block. Appropriate = remove in summer, install in late fall, and always pay attention to ECT on your UltraGauge or ScanGauge.

My HX gave me a lot of frustration (3 years worth) till I started using Marvel Mystery Oil in the fuel. Bottle recommends 4 oz per 10 gallons. I use 2 oz per 10 gallons. You might try it at 4/10 gal when you first use it. I and also turborvr1991 both found it improving lean burn behavior over the first few tanks with MMO, and then settled in to pretty stable "good behavior" after a while.