Most cars these days the body will fall apart around the engine.
There are exceptions... stuff that eats head gaskets... or is pushing around more weight than it can produce torque to push.
The Diesel Mercades mentioned in here is a shining star... people have broken a million miles with them.
The big deal is replace it before it wears out. Not the car... the part. You have to keep an eye on things like ball joints... shocks, brake pads etc.
To keep the mechanicals lasting a good while, you have to keep the oil changed. Cut open the filter and check for metal particles. Send the oil out for testing if you find any metal. This tells you if its a babbit bearing... or if its the rings... or if your eating something else thats not normally eaten!
Oil keeps stuff from rubbing, but some stuff does rub! Lifters ride on the cam. Rockers ride on the springs and pushrods on a pushrod V8.
If you WANT it to last forever you have catch problems before they break. Its not so much preventative maitenance, but catching something before it causes a big problem. Like getting water in the differential! This causes lots of problems. You have to keep them CLEAN to see the problems.
Diesel is the way to go for long life, but even then you have to find a body to wrap around it that will last. It'll be the heaviest... slowest... most in-efficient vehicle, but you have to find the one that is NOT loaded when running around. You need to be able to lope the thing around at idle and not stress anything. When you start stressing a motor... you create more heat. HEAT kills. Detonation kills bearings, bearings that are killed wear the crank/rods... which gets enough metal crap in the oil to wear the rest. The transmission needs to be a manual... thats well known. You need LOTS of oil capacity on everything! Oil has a load limit, you cant absorb but so much heat into oil, and over heating it causes viscocity cut... which makes you have trouble keeping everything apart.
The other thing, if you are building a car to last forever... you have to build it like a boat. The electrical wiring has to be tinned... shrink wrapped and kept from moving. You cant have an electrical short... or a location where you can get corrosion. You kill alternators trying to charge a slow discharge... Water pumps. Not much you can do with these but check the weep hole often.
Hoses/belts. You need to think about getting some blue goodyear hoses, they are supposed to last forever. The cooling system needs to be flushed every 2 years... and the coolant replaced. The coolant is your anti-corrosive liquid for the cooling side of the engine.
Belts, If you go with something that uses serpentine belts, you'll need to keep some on hand. Use the company that made the cars brand belts. Often motorcraft/acdelco and honda parts go on easier... and last longer.
I do not like timing belts. They get cracked... break... and on zero clearance engines cause major damage. For me, if I was to build something to last forever I would use a gear drive setup. Chain is ok, but they stretch.
You also have the fuel system to worry about. Filter the fuel before it goes into the tank if its important to ya. Use some low micron high flow filters if you need the high volume of fuel. Replace your steel fuel lines with stainless.
Use stainless AN rated line to connect when you need flexible lines. For mechanical pumps... use your brand name pumps... try for American made. For electric... well, its electric!
For your frame. YES frames do flex, they do eventually deform. Old pickups that have been over loaded sag! You'll want to have the frame boxed, powder coated or painted... then undercoated till you have to scrape the goo off of bolts before loosening!
Brakes... well these are consumables! You can pick to erode your pads, or cut your rotors... Metalic pads cause ya to cut the rotors. On german stuff the steel is so soft that they dont last real long to begin with. Try to find USA/canada made rotors if you can! I like disks, less moving parts in the package.
Use GOOD grease on your wheel bearings and to grease your chassis. You want to have all the zerk fittings written down... and keep them greased, but not so much that they dont seal.
Air filters. K&N makes a nice filter... the off road guys run a foam filter wrap... says enough to me that if you can use one... do.
Exhaust system. Stainless steel! You only buy it once, but you put up with the popping when its expanding and contracting. Make sure the muffler you install is ALL stainless.
To keep the interiour looking nice you have to keep it garaged. The plasticizers in late model cars leach out with the heat from the exposure to the sun. Tint can cut down on the UV rays, which only come in... and cant go out. They get absorbed by the materials in the car... causing it to act like an oven. Some states let you tint the windshield, others dont. Use a reflector if you cant in your state. Keep the carpet clean, shampoo it every once in awhile... your goal is to keep the dirt from working into the mat of the carpet! You dont want the dirt in so deep that it wears out your carpets. For a survivalist type vehicle, I would do a truck bed liner on the whole interior.
Tires. Keep them inflated, make sure they have enough belts to support the weight of your car. A stiff enough sidewall not to roll under while turning (Decreases rolling resistance as well!)
Again, I'd be looking for a relatively stripped full size sedan with either a big cubic inch low compression gas, or low compression naturally aspirated diesel.
If you dont like technical stuff... stop here
What you ALSO need to think about, is what RPM you run while cruising. Will you be doing highway miles, or will you be going around town? What does your torque band look like? Your volumetric efficiency peaks around the same point that your torque band peaks. You want a WIDE torque curve for a long lasting vehicle. If a sports car is peaky, like a motorcycle... you want a tractor. You want to be able to shift the car into overdrive... be sitting on your engines most efficient rpm for the speed. You cant gear it so the car does 60 at idle, you would tax the engine. You can however build a motor to peak the torque curve at around 2000... and use the gearing to get your rpm to 2000.
In doing this, you reduce your cruise rpm. Which reduces your number of revolutions per mile. Reducing your revolutions per mile... effectively reduces the number of miles your crankshaft turns... along with rest of the engine and transmission. If your vehicle can do this without bogging down. If the oil preasure is high enough to keep the motor alive... and you have no concerns (IE the motor pounding like a lawn tractor going up a hill!
) Your set on that count.
The next thing to think about is the tire size. To wide, and you have rolling resistance. To skinny... and your handling deminishes. If your only goal is a long lasting car you need some hard tires that dont deform with little tread wear. This makes for a ride like a buckboard, and handling similar to a shopping cart. You also need to remember to keep the air preasure in your tires within a couple pounds of the recomended preasure on your drivers door.
If you've succeeded at this, you can go to more time intensive modifications.
You can lower the front end of your car so less air goes under the vehicle. The rake that occurs when this happens (given the car is slammed...) would give some downforce. We dont want you to high-center on a speed bump though! For all intents and purposes your trying to lower the drag. Some of the import people use a spoiler on the front of the car, the old muscle cars ran two different size tires... and drop springs on the front. Late model cars have electronically controlled suspensions that lower at speed... they all try to do the same thing! (or at least thats the REASON, many people go for the looks!)
If you can reduce the load on an internal combustion engine, you reduce the heat output. Eventually you get down to where the combustion process limits the lessening of heat production. It takes x number of gallons per hour to run a motor. You cant go less than that number because you have an air to fuel ratio that you have to keep at the right point... if not it runs rich and loses power. Or runs lean and eats its self (Melts pistons, destroys exhaust valves.) Figuring this out is the tough part (in-exact science if you will...) which is why we measure the consumption of larger engines in miles per gallon, than btu's per cycle!
I leave you with this:
Dont ever tax your engine beyond 80% of capacity.
Dont forget to change your oil.
When something breaks, fix it... and improve on it.
When you have free time, grab a book about your car... and review it.
When pay day comes, go get some tools.
http://www.chiltonsonline.com/
http://www.haynes.com/
