Is it worse to start and stop your car, or let it idle? I just got my first new car in many years and I got all obsessed with mileage, although not to the point of hypermiling, like to the point where I'd shut it off in a restaurant drive-up or while sitting in a car wash. My question is, which is worse? Should I let it idle for five minutes or stop and start it twice in five minutes?
I've learned on this board that idling can cause fuel dilution but also that frequent starts and stops cause engine wear. I suppose if I let it idle a few minutes I'm going to drive the rest of the way home and burn off any diluted fuel? Did I just answer my own question?
What's worse (for car AND oil)?
- Thread starter ruxCYtable
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I guess that makes sense. Since it's not a "cold start" I'm probably not causing any engine wear if I'm doing it after reaching operating temp. Any other thoughts?
Taxi's and cop cars idle all ady long. Taxi's often reach 400k+ on the original engine.
Idling leads to fuel contamination and thinning (duel to fuel and moisture). It means you probably need to change the oil more often. As we've talked about here before, probably not much harm in the oil being a bit thinner -- the requirements for an oil at low RPM and no load are fairly small.
Originally Posted By: Chris142
Taxi's and cop cars idle all ady long. Taxi's often reach 400k+ on the original engine.
Originally Posted By: tpitcher
- What are the taxi drivers or their maintenance plans doing that consumers are not doing?
- What bad driving habits or maintenance plans are consumers doing to limit their engine life that taxi drivers & their maintenance plans are not doing?
RuxC, congrats on the new car!
Myself, in the same type situation(driveup window), I like keeping the engine warm. In the summer I may/may not turn off the engine but in the colder temps, I'll keep'er running!
The way I understand it(Hybrids) is that these type of engines that start & stop frequently are designed to do so, "differently" than our normal combustion engine. I can't answer as to how they're different. Maybe someone in the know will chime in on this in particular.
Engines isn't something that I have ever had issues with in any of my vehicles wheather letting them idle for long periods of time, or starting/stopping...Ever! And this includes engines with several hundred K's of miles in vehicles into their teens(close to 20 yrs old). Well, I did have some issues with my '68 BUICK!
Although I try not to do this, in many, many occasions, I've let my engines idle in the driveway in the winter time for close to an hour while cleaning the snow from the driveway/steps/walk and have forgotten the cars were running, especially cause the snowblower was running too...OOOPS!
And I have done so many short trips(winter/summer) jumping from store to store, bank, fast food drive window, quick visit to a friends house or several friends/family etc. It was actually the starter I'd was more concerned with. I can't even count the startups I made on those trips. Never worry!
ruxC, if MPG is your concern, I hope you bought a car with good MPG/EPA rating to start with! The Elantra in your signature seems to be on the right track... 
I've had vehicles with 340,*** miles on'em @ 18 yrs old and if the engine wasn't running @ optimum, it was related to vacuum or fuel system and I may not been able to cure/find it and at that point, I didn't care anymore! But the issues with any of my older high mileage engines WERE NOT due to long idling or lots of startups.
Originally Posted By: brentalan
Well they have all these new cars and hybrids that are "stop/start" where the engine shuts off at stop lights and what not.
As a result, I would assume stopping/starting a warmed up engine is not a big deal.
I've had vehicles with 340,*** miles on'em @ 18 yrs old and if the engine wasn't running @ optimum, it was related to vacuum or fuel system and I may not been able to cure/find it and at that point, I didn't care anymore! But the issues with any of my older high mileage engines WERE NOT due to long idling or lots of startups. Originally Posted By: ABerns
I've always thought these commercial vehicles got so many miles because they had fewer heat cycles - going from cold to hot. Start a taxi up, it's going to run for 8+ hours. Start an average person's car up, it'll run for what, 20 minutes on average? This is where the wear is happening.
Speculation, of course. Anyone else?
Originally Posted By: ruxCYtable
I've learned on this board that idling can cause fuel dilution but also that frequent starts and stops cause engine wear. I suppose if I let it idle a few minutes I'm going to drive the rest of the way home and burn off any diluted fuel? Did I just answer my own question?
I just read last week that letting your car idle for more then 15-30 seconds on a NEWER vehicle is a huge waste concerning fuel and engine wear...
I've read this many times, from many different sources and article publishers that if you're going to be idling for more then 1 min, it's better to shut off the engine, esp if it's already warm.
A warm restart is much easier on both the starter and anything else for that matter. It doesn't cause any wear since the engine is up to temp and the oil is still all over the engine lubricating it instantly upon restart.
I don't shut off my car in drive-thru's simply because you have to move a bit as every car in front of you leaves every 30 seconds so it's just pointless.
Car washes or if somebody runs inside a convenience store real quick, i shut it off.
My 98 Camry V6 is on it's second starter @ 214,000 miles (changed the first @ around 60k due to mechanical failure) and it sees nothing but cold starts 3-4 times daily 365 days a year.
Originally Posted By: Boss302fan
I just read last week that letting your car idle for more then 15-30 seconds on a NEWER vehicle is a huge waste concerning fuel and engine wear...
Drive Thru? Like for a Soda? For goodness sake park your car, Shut off the engine, and WALK in for your drink/food.
You don't need to burn that gas
You DO NEED to burn those calories.
I haven't gone thru a "drive thru" since about 1970.
Originally Posted By: Char Baby
RuxC, congrats on the new car!
Myself, in the same type situation(driveup window), I like keeping the engine warm. In the summer I may/may not turn off the engine but in the colder temps, I'll keep'er running!
The way I understand it(Hybrids) is that these type of engines that start & stop frequently are designed to do so, "differently" than our normal combustion engine. I can't answer as to how they're different. Maybe someone in the know will chime in on this in particular.
Engines isn't something that I have ever had issues with in any of my vehicles wheather letting them idle for long periods of time, or starting/stopping...Ever! And this includes engines with several hundred K's of miles in vehicles into their teens(close to 20 yrs old). Well, I did have some issues with my '68 BUICK!
Although I try not to do this, in many, many occasions, I've let my engines idle in the driveway in the winter time for close to an hour while cleaning the snow from the driveway/steps/walk and have forgotten the cars were running, especially cause the snowblower was running too...OOOPS!
And I have done so many short trips(winter/summer) jumping from store to store, bank, fast food drive window, quick visit to a friends house or several friends/family etc. It was actually the starter I'd was more concerned with. I can't even count the startups I made on those trips. Never worry!
ruxC, if MPG is your concern, I hope you bought a car with good MPG/EPA rating to start with! The Elantra in your signature seems to be on the right track...
I've had vehicles with 340,*** miles on'em @ 18 yrs old and if the engine wasn't running @ optimum, it was related to vacuum or fuel system and I may not been able to cure/find it and at that point, I didn't care anymore! But the issues with any of my older high mileage engines WERE NOT due to long idling or lots of startups.
Originally Posted By: brentalan
Well they have all these new cars and hybrids that are "stop/start" where the engine shuts off at stop lights and what not.
As a result, I would assume stopping/starting a warmed up engine is not a big deal.
I've had vehicles with 340,*** miles on'em @ 18 yrs old and if the engine wasn't running @ optimum, it was related to vacuum or fuel system and I may not been able to cure/find it and at that point, I didn't care anymore! But the issues with any of my older high mileage engines WERE NOT due to long idling or lots of startups. Originally Posted By: Artem
I don't shut off my car in drive-thru's simply because you have to move a bit as every car in front of you leaves every 30 seconds so it's just pointless.
Originally Posted By: ammolab
I haven't gone thru a "drive thru" since about 1970.
This thread has blown my mind. Shutting your engine off vs. idling for a minute or two seems...like a no brainer. The amount of fuel dilution in that time period on a new motor has to be almost non-existent and driving the vehicle for another 20 mins is going to burn that off quickly.
Originally Posted By: TFB1
Originally Posted By: ABerns
I've always thought these commercial vehicles got so many miles because they had fewer heat cycles - going from cold to hot. Start a taxi up, it's going to run for 8+ hours. Start an average person's car up, it'll run for what, 20 minutes on average? This is where the wear is happening.
Speculation, of course. Anyone else?
Originally Posted By: ruxCYtable
I've learned on this board that idling can cause fuel dilution but also that frequent starts and stops cause engine wear. I suppose if I let it idle a few minutes I'm going to drive the rest of the way home and burn off any diluted fuel? Did I just answer my own question?
Injected engines running properly don't dilute oil soenough that it causes a problem. The question is... do you like buying starter motors and/or ring gears?
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