I remain a little confused by 'thinking outside the box' and 'not my car.' Is this a real, 'I have the title' car or a day-dream car?
If a real car, how about some specs:
- make/model
- in-service miles
- engine
- transmission
- wheels and tires
- instrumentation
- MPG at xx mph over a 10 mile flat route, no stops, both directions
Now thinking 'outside the box' is often helped by understanding the box:
- rolling drag - a function of tires, bearings, and transmission friction
- stirring drag - a function of transaxle lubricant
- aerodynamic drag - a function of shape and cooling air flow
- thrust - what the engine power provides
- brake secific horse power - a measure of how much power (for thrust) as a function of fuel burned ... often badly measured on a test stand without accessories including the water pump.
- accessory load - the amount of power sucked from the engine to provide 12V power, power steering, power brakes, air conditioning, and any other parasitic energy drains
Before leaving 'the box,' consider the basics:
- tires - low rolling resistance and 4-wheel alignment. Sumitomo T4s are low rolling resistance and have a maximum sidewall rating of 51 psi, excellent for lower rolling resistance. Oversized, they can provide 2-6% overdrive without making a single mod to the drive train. But at least pump up the tires to the maximum sidewall.
- lubricants - not just engine but also include the transmission and if it has one, differential. Try to drop any pans and access holes and clean out the gunk. Then drive 1,000 miles and do a second chance to get rid of the 15-25% carry forward from the previous change.
- spark plugs, air filter, and PVC valve
- throttle body cleaning and injector cleaner
- disk brakes - make sure they only lightly brush the surface
Now baseline your car performance by using any of the web-based, mileage recording systems: Fuelly, Ecomodder (of course), fueleconomy.gov. If you do not have these, get quality instrumentation:
- ScanGauge or equivalent mileage instrument - I prefer recording systems so I don't have to memorize the data.
- GPS with recording capability - Garmin nuvi is good but there may be others. This is needed to get true mph as well as terrain emphermis and actual driving routes and patterns.
Benchmark your perfectly tuned car against your real world driving. Use this data, analyzed at home on your computer as if you are analyzing a stranger's data. Select a series of hypothesis and test each one, one week at a time. Folks have already offered various hypothesis to which I would add these specific to the engine:
- replace mechanical water pump with electric - with a good controller, it will only draw power as needed to cool the engine allowing faster warm-up and lower overall power drain.
- hill billy plug-in - use 24V, deep-discharge batteries charged up at night that feed a 12V (actually 13+V) power supply to offload the alternator.
- body, air inlet block - some form of inlet air block so the minimum amount of air enters for the conditions. More blocking in the winter and high speeds. Less blocking in hot weather and low speeds.
- tire overdrive - largest, low rolling resistance, maximum sidewall pressure tires that will fit.
- air dam and side skirts - to reduce under body drag.
There is a lot of space 'inside the box' and once you've gotten the car to walls, then it is time to go outside the box ... with a high efficiency, hybrid. This is called shreding the old box and getting a better box.
Bob Wilson