What are the 5 gear ratios in the T5? Tire size? As Jerry said, more facts are needed. How often is it driven?
I've spent about 8 or 9 weeks studying the Rochester B and BC carburetors and roughly 5 weeks studying the Carter YF models. Through it all I've remained as objective as possible and I promise this was not simply drinking beer, looking at the carburetors and scratching my head. I was as thorough as possible...read as much data as I could find, measured everything I could, compared this/that, talked to several knowledgeable people, built jigs, straightened castings, etc, etc. And at the end of the day: There are aspects of the Carter design that make it a better scheme if running leaner, more smoothly and with better gas mileage are important things to you. But there are aspects of the Rochester that might be appealing also. If you are driving the pickup very infrequently, the gas in the float bowl will evaporate and this will not be good for the Carter accelerator pump. Getting wet with ethanol gas and drying out will cause it to crack and go bad. If that's the way you're driving, I'd say you'd have less to worry about with a Rochester.
And Joe is 100% right. Example: If we drive our Subaru Forester at 57 mph on a relatively flat road with no wind, our gas mileage will be as much as 42 mpg. If we drive at 65 in a crosswind we will get 32 or so. If we're driving into a headwind at 65 mph we can see it go to 27. Big swings.
Now for more about gasoline. Ethanol gas (evidently no matter where it is stored) will undergo changes over time. And these are not good changes. I believe they would affect your gas mileage, spark plugs, valves, performance, etc. Take a look if you're curious:
http://i1154.photobucket.com/albums/p535/JonGoodman/MVC-727F.jpgThe vial on the left is gas right out the pump. The vial in the middle is gas removed from the gas tank of my pickup (vented cap, naturally). It had been in there for 6 weeks or so and the tank is new...a galvanized tank made in Canada. The vial on the right is some gas I poured from the 2 gallon plastic gas container I use with the lawn mower. It had been in there about 2 months or less. The left one is pretty clear. The others look more like strong urine. If you take these darker ones, pour a tablespoon or so into the divot in the bottom of a soda can and light it, you'll see a fire burning with heavy black smoke and a lot of soot. A nasty fire like a wellhead fire. I should have taken a picture of it. It also burns more slowly and the residue left is dark brown and sticky...almost caramelized looking. If you do the same with the fresh gas, it will burn with less smoke and it seems to burn more a bit more rapidly. There will be notably less residue left. Naturally you might think the darker ones are evidence of evaporation causing a concentration of the crap that is now in the gas, but the lawn mower jug isn't vented, it is plastic and there's not much there to react with gas. So I can't say if the air in the jug (and gas tank) exacerbate this change or not but the change definitely occurs and the old gas is not good.
