We all know about the car salesman who tells you that the previous owner was a little old lady who only drove it to church on Sundays. This is always made out to be a good selling point. But is it? I’ve heard that driving short distances, and leaving the car sit for a long time is bad for the engine. So what’s the straight skinny on this?
The reason I ask is because I sometimes don’t drive my car for a couple weeks at a time. And I rarely make long trips. It is parked in the street exposed to the elements.
Am I okay, or should I change my driving habits?
Battery drain is a concern only if the car is parked over a month:
As far as exposure to the elements, most people don’t have garages so you are part of a big club.
A couple of weeks of sitting is not bad. Over months you might need to add fuel stabilizer to your tank, but a couple of weeks is fine.
Short trips, however, are indeed bad. When you drive it every two weeks, take the scenic route home.
When you start a cold engine, two things are happening:
#1: cold-start enrichment. When fuel is injected into a nice warm intake manifold, it evaporates (nearly) completely before being drawn into the combustion chamber; this means the computer only needs to inject enough fuel to make a combustible mixture. OTOH, when fuel is injected into a cold intake manifold, it doesn’t evaporate completely; this means the computer needs to inject extra fuel to compensate. That extra (liquid) fuel doesn’t burn; it gets drawn into the combustion chamber where some of it splatters on the walls, and some of it vaporizes (from the heat of combustion) and goes out the tailpipe as raw hydrocarbons. The liquid fuel that splatters on the combustion chamber walls dilutes the motor oil that’s there and compromising its lubricative properties.
#2: poor piston/ring/bore fit. In a cold engine, the piston and its rings fit poorly against the cylinder walls, making a leaky seal. This allows high-pressure combustion gases to leak past that seal, carrying combustion products (including copious amounts of water) and unburned gasoline down into the crankcase, where they blend with the motor oil.
The oil has emulsifiers to help cope with this stuff: put a drop of new motor oil on your finger and rub it under tap water, and you’ll end up with a milky-white emulsion. It also has additives to help neutralize some of the more corrosive combustion-derived components of that blow-by. But it only has so much, and can only cope with so much. If you drive your car long enough and at high enough speeds (e.g. a 15-mile highway cruise) to get the engine good and hot, you can boil the water and fuel out of the crankcase oil, but much of the troublesome combustion byproducts will remain.
What’s a church driver to do? Change your oil more frequently. How often? Check your manual. Many cars recommend different oil change intervals depending on how the car typically gets used. Got a 20-mile highway commute? Your oil is probably good for 7000-8000 miles. Got a 5-mile city commute? Your car should be OK if you change your oil every 3750-4000 miles. Again, those are ballpark numbers, and you really should check the owner’s manual for your particular make/model.
A car that never gets out on the highway and never sees hard acceleration may also see some buildup of carbon deposits in the combustion chambers due to low combustion temperatures. If this goes on for a long time it can cause some pinging when someone does finally put their foot to the floor, but it can be cured through some combination of fuel additives (e.g. Techron) and the classic Italian tune-up (i.e. drive it like you stole it).
TL,DR: a life of short trips isn’t necessarily bad, provided you change the oil in accordance with the manual’s recommendations for how you operate the car.
Sitting for a couple of weeks in between trips isn’t a big deal. As long as your battery is healthy (consider replacing it every five years), it should hold a charge for that much time.
I agree that the effect on the engine isn’t terrible compared to other cars (I mean, you’re going to have to go through the cold start no matter how far you drive after that) but what about rust in the exhaust system from unevaporated water?
A critical point is whether the engine gets fully warmed up when it is driven. If it doesn’t, it should have the oil changed more frequently than even the “severe service” schedule calls for. If it does get fully warmed up, I wouldn’t worry.
:smack: Good point, I totally forgot about that. Buyers of church-commute cars should anticipate that the car will need a new exhaust system sooner than a highway-driven car would. The difference is even greater in cold climates: you can often see recently-started cars drooling liquid water from their tailpipes when they pull away from stops. It takes a while to heat the exhaust system enough to evaporate all that water.
Thanks all. Good advice about the oil changes. I’ll try to stay on top of that.
I’m not sure if anyone else tossed this in but I would add a fuel stabilizer (I use Sta-Bil <sic?>) to the gas. If you aren’t driving a lot it won’t add to your cost much and with some places being E-10 year round and talking now about going to E-15 it helps. It is more a biggie if you are parked for weeks/months though.
Pretty much what Machine Elf said, but I’d add that I’ve always found that people are if anything too conservative in adhering to mileage-based maintenance schedules but for whatever reason virtually never keep the time-based ones. So if you’re looking at, say, a 5 year old car with 10,000 miles on it there’s a pretty good chance it’s only had maybe one oil change and that’s it, regardless of what the owner’s manual says. I personally think that a car with excessively low mileage for the age is just as bad is one with excessively high miles. Maybe even worse.
A co-worker of mine bought a very low mileage (<25,000 miles) 1998 Cadillac a few years ago. The seller claimed it belonged to his grandfather that drove the car to town once a week and used it for a couple trips to California. Within 3 months of buying the car the transmission crapped out due to dried out seals. He also had lots of other little issues with the car. After owning it for less than 2 years and about 12,000 miles, the transmission crapped out again. He traded it in for a new car. Didn’t get a whole lot for it either.
It may need some catch-up maintenance, there may be body rust, but the drive train should be in great shape, a car actually like that can be a great deal. Problems could be old tires, old brake pads, cracking hoses, dried out gaskets, carb or injector gunk, water in the fuel tank/lines, and pieces of hard candy in the ashtray.
It’s very bad if it’s a diesel with a filter fitted. The filter needs to get up to temperature to work properly and if you don’t let it get to temperature it will eventually fail. So take your diesel and give it an occasional thrash!
Another one is, "The engine was recently replaced, but it came out of a Corvette! "
I’ve always wondered where all these Corvettes are without engines…
Another problem with low-mileage cars is they may not be driven enough for defects to become obvious. I bought Airman’s grandfather’s 2003 Honda Accord. The mileage was very low and it wasn’t apparent until it was driven every day and on 3000-mile road trip that the transmission was defective.
That said, the Accord was replaced by a Civic that was also driven by a little old lady. I never learn.
From wrecked Vettes. Given the car and the kind of people who own them, they have to be relatively common.
The real question is: how come so many wrecked Vettes still have usable engines???:dubious:
The GM engines of the LS series like the LS1 were in the C-5 Corvettes, the LS2 is in most C-6 Corvettes, etc.
But these LS and before them the LT series of V-8 engines were also used as the V-8s in all the other GM cars built during the same years.
A little bit different cams, a different intake manifold, but essentially the same engines went into Corvettes and also any other GM V-8.
The “I’ve got a Vette engine” really just means, I’ve got a GM V-8 that might have come from a Vette, or a Malibu SS, or a Camaro, or an older Firebird, or pick your model.
Most Vettes did not have an engine built specifically for the Vette. With the trend away from performance GM V-8s it may be true now.
To elaborate a little more.
My 2002 Pontiac Trans Am Firebird has the 5.7 Litre LS1 GM engine that also came in the C-5 Corvette. The C-5 was made from 1997 to 2004. The Trans Am was discontinued in 2002, I have one of the last year.
GM ran out of, or didn’t want to make more, parts for the Trans Am. So all LS1 engines in these 2000 to 2002 cars also had the C-6 intake manifold, 25% of the final year cars also had the C-6 block, which just means that there were slight changes in the internal engine block that allowed better oiling between cylinders. No power advantage at all.
So I have a mostly stock 2002 Trans Am with a LS1 engine, with an LS6 intake manifold, with a LS6 aluminum block.
And it is still a (mostly) stock 2002 Pontiac.
No Corvettes were involved, but these issues allow small minded people to say, “it’s got a Vette engine in it!”.
Let them boast, if that is all they have got.
That’s a very good point. Engineers sometimes describe reliability as a bathtub curve where a given product is most likely to experience failures near the beginning (as manufacturing defects become apparent) and near the end (as it wears out) of its useful life. If you’ve got an ultra low mileage older car, it may still be in the part of its life where you’d expect to see manufacturing defects, but the warranty that normally protects you from those has expired due to time.