Blogs Car Info Our Show Deals Mechanics Files Vehicle Donation

Warming Up Your Vehicle

I just read Tom and Ray’s column about warming up a car. I understand why fuel injected engines don’t need to be warmed up, but even the newest motorcycles that come with carburetors have a manual choke and tell you in the owner’s manual to warm it up for a minute or two, even in warm weather. So, what’s the deal with older carbureted engines? Is it really a good idea to start it and go? Should you give it a short (1-2 minute) warm-up in your opinion? Tom and Ray only said not to give it an extended (5-10 minute) warm-up. They didn’t say not to warm up an older car in nice weather for one or two minutes. What do you think?

Tom & Ray are right, as usual. A car with a carburetor and choke needs a little longer to start running smoothly so you have enough power to head into traffic. My last carbureted car, a Chev Caprice, needed about 30 seconds or so after which it ran smoothly enough to take off. In other words, the same rules apply; a car warms up fastest when it has some load on the engine. In all cases, make sure you can see out the windows on a cold morning!

In the cars I owned with both manual and automatic chokes, I would let the oil pressure come up to the normal range and then drive slowly. As the temperature gauge would rise, I would increase my speed. With the manual choke, I would push it about halfway in after the engine started and then gradually push it all the way in as I drove. I did have a 2 cycle LawnBoy mower that was made in the mid-1950’s. The instruction manual said on a cold engine, to put the engine on full choke, then push the choke to the halfway position when the engine started, idle the engine for a minute, and then open the choke fully. I assume that one runs the mower under full load at full speed immediately where this isn’t the case with a car. Maybe the motorcyle companies anticipate that the motorcycle driver will run at full throttle immediately after starting the engine.

I appreciate your input, but you seem to be contradicting yourself.

You say Tom and Ray are right. They say “start it and go.” If Tom and Ray were right, your Caprice would not have needed 30 seconds.

Your answer seems to fall into the middle ground.

I am not here to split hairs! Your question dealt with 5-10 minutes, or 1 to 2 minutes. Most people will take a while to put on their seat belt, ajust the mirror, etc. That time will easily take 20-30 seconds!!!

In Minnesota in the winter you may need several minutes to clear the windshield, so you can see out.

Tom and Ray suggest that lenghty warmups are not necessary. I AGREE!!. Tom & Ray do not advocate turning the key and then immediately burning rubber on takeoff!

The 20-30 seconds is good for the engine to get the oil circulating to the valve gear.

After that, you drive off gently until the temperature gage starts moving, then you can blast away. If you are a jogger your body will need the same procedure.

Trust this explains the general philopsophy about tender loveing care of cars.

Relax, dude. I posed the question because I see a distinction between “start and go” and “warm it up for a minute” and I only followed up because I wanted your opinion about the distinction. Don’t blow a blood vessel in your brain just because I am interested in your opinion. Let it go. I will engage in civil discussion with someone who isn’t so touchy.

Come on guys we are buddies… Everyone interested in the wonderful engine and tyres world…Some more experienced than other but all willing to help…I am learning a lot with all of you!

I’m not sure there is a single “correct” answer for all engines with carburetor. I have driven some that are ready to go after a few seconds and some that are very finicky for several minutes. The most temperamental I’ve had is a VW/porsche with multi-carburetors and no choke/tickler at all, that engine is difficult to keep running at all for several minutes. My motorcycle with duel side draft carbs and a manual choke is drivable after about 30 seconds with partial choke, but not really happy for 2-3 minutes.

You can come up with your own theory here. The differences of opinion are all over the map. Even if you don’t come up with a great automotive theory, I’m sure it won’t hurt anything if you have a feeling that you’re doing the right thing despite all this semi-relevant opinioning. Whatever I mean.

That is exactly why I brought this up. I thought it was strange that Tom and Ray said that you should always get in and go regardless of what you drive.

I think Tom & Ray assume that when the engine runs, it should be reasonably ready to go. Years ago when gas was cheap, and air pollution not an issue, people started up their cars in the driveway, and went back inside for a coffee. So we got used to lengthy 10 minute warmups. These warmups were for human comfort, but did the engine little good. But with balky carburetors, some warmup was needed to get the engine to run smoothly.

When my 1965 Dodge Dart was new, I lived in an apartment right beside the freeway which was on the way to work. If I parked the car outside in the winter, I could not head out into traffic with the choke still on; the car would just sputter. That car needed a minute or so to start running smoothly.

Today, the engine computer takes care of the air/fuel mixture and we can drive off as soon as the oil cicrculates to all the bearings and other moving parts. Just the same, a cold start equals 500 miles of driving in terms of engine wear.

“That is exactly why I brought this up. I thought it was strange that Tom and Ray said that you should always get in and go regardless of what you drive.”

They are probably also assuming that 99% of their listeners are driving relatively new fuel injected cars.

The long warmup is/was needed for two reasons:

  • Before we had multiviscosity oils, taking off too fast damaged the crankshaft bearings.

  • Around here, we have freezing rain. Trying to chip that off the windshield can damage it. So the defroster is needed to melt it.

Because of this second effect, daylight-saving time uses more gasoline in states where this happens in November and March.

Another adverse result of ‘start and go’ is high speed glazing. High-speed glazing is a varnish-like coating on the interiors of cylinders that, despite its lubricating qualities, diminishes ignition spark intensity because of its electrical conductivity. Essentially, it shorts out the spark plugs. This results in incomplete combustion of fuel, and produces soot- an abrasive. Soot contacts the cylinder walls and piston rings on its way to the oil pan, so it does damage before it can be collected and filtered. This abrasion reduces compression, and thus, efficiency, forcing the driver to rev the engine higher, repeating the vicious cycle. To quote Shakespeare, the problem ?grows by what it feeds upon.? The end result is what Tom and Ray call WBBB: Wicked Bad Blow-By, a looseness that causes excessive pollution and excessive consumption of fuel and lubricating oil, and therefore, excessive consumption of crude oil.
One may argue that a simple spark plug change would fix all this, but that suggestion is ineffective for two reasons: one, people tend to be cheap and strictly adhere to their owner’s manual maintenance schedules, for better or for worse; and two, people tend to continue behavior patterns long after their relevance expires. Another good example of this is the oft-told story of the new housewife who cuts off the ends of the roast before cooking because her grandmother’s roasting pan was too small.
By contrast, in a hybrid vehicle, engine load is somewhat isolated from operator demand. The engine starts when the batteries need to be recharged. This means a driver can set the vehicle in motion, on battery power, immediately after all occupants and cargo are secure, and not cause high speed glazing. The engine would likely start when the vehicle is well underway, at which time operator demand would be far less than it would be when accelerating from a dead stop. Although a gentle driver cannot positively influence a hybrid’s durability and reliability, by the same token, a yahoo can’t negatively influence it, either. That is a good thing.
As technology advances, motor vehicles get increasingly, though never completely, idiot-proof.

As technology advances, motor vehicles get increasingly, though never completely, idiot-proof.
P.S. The previous is not an endorsement of idling for more than 5 minutes, in violation of a 1972 Massachusetts law. Short idling is necessary to ensure adequate lubrication of moving parts before driving. If one applies Thevinin’s Theorem, or something like that (from EE), to engines, the power dissipated (heat produced) in the source is related to the power consumed at the load: driving (gently, of course) will produce more heat in the same time than idling. This works up to a point- the Maximum Power Transfer point, beyond which (when source internal resistance exceeds load resistance) the power at the load starts decreasing. Fortrunately, motor vehicles and their engines are designed so that the MPT point would never even be approached.
Much of this (save the theory) is likely in your owner’s manual, so follow it.

My 2002 Toyota Sienna apparently has the computer designed so when one starts out cold, it resists mightily any attempts to go racing off. It takes a lot of throttle to make it go fast until it gets warmed up. It also hesitates to shift up when it is first driven. Other Sienna owners have reported the same thing, though I have no proof all of them do this.

So, in simple terms, you confirm that first we need to circulate the oil properly. Then drive off gently and gradualyy increase the load on the engine (speeding up) to avoid this nasty glazing.

For many years I have used a block heater and synthetic oil. The combined effect is very rapid lubrication for all moving parts. Bu I still take off slowly until the temperature gage moves up.

The last high mileage car we sold had 350,000 miles on a small block V8 and the oil consumption was very low. Compression was 100% on 6 cylinders, 96% on one and 94% on the remaining one.

Well I have messed around with all types of car my whole life. I also went to collage to further my knowledge on them. And the way I was tought both ways was to always give your car plenty of time to get the oil pressure up so that everything is coated in oil. You definitely do not want any metal to metal contact whether it be new or old injected or carburated. Even on a hot day I like to let one run for atleast 2 or min. But that is just what I think!

Good summation! Whether it is 30 seconds or 2 minutes, the imoprtant hting is to make sure everything has oil. If it is cold, and you don’t have synthetic oil, you may need the 2 minutes.

With the environmental hype, we are under pressure not to idle; some idle will always be necessary. How lon depends on the ambient temperature and the weight and type of oil in yor crankcase.

Another adverse result of ‘start and go’ is high speed glazing. High-speed glazing is a varnish-like coating on the interiors of cylinders that, despite its lubricating qualities, diminishes ignition spark intensity because of its electrical conductivity. Essentially, it shorts out the spark plugs.

Now wait just a minute. Are you trying to say this “glazing” is more conductive than the metal it is coating? Most cylinders are metal and very conductive. I’m not saying glazing on the cylinders is a good thing, just that this conductivity idea is bogus.