My newly bought 2013 Silverado hybrid gets 16 mpg city with very careful driving and will not stay in EV mode like it is supposed to do. It should go to 30 mph with careful driving as specified. This car turns the engine on at 0 to 10 mph from a stop on level streets with very minimal gas pedal pressure.

A forum contributor says they get 21 to 23 mpg city so I am convinced that my vehicle has a defect. Can anyone give me an idea of what might cause the vehicle to start the engine too quickly?

 

What is your "regular" drive distance per "key cycle"? Short? Less than 5 miles?


Staying in EV longer does not mean better fuel economy. The HV battery is sized to store Regenerative Power during braking. Then supply system power while stopped and some electric boost for acceleration.


Aggressive stops exceed battery power limits and just make hot brake pads.




A dealer scan tool can take data from the HV battery and the hybrid system.
Fuel economy on a 3 Ton hybrid is a combination of stopping and going.

 

I use the built in data for MPG. My key cycle might be 5 to 20 miles, but I make sure to start measuring with a warm engine. The engine will use 100% boost on the meter for strong acceleration with the gas engine, but only about 5% boost on start from 0 MPH. That means that it is nearly impossible to get past 10 MPH without the gas engine. I can use gas to get to 25 and then slow to 20 to get into EV mode. But the gas engine comes on with hardly any electric boost. Also I do not get near the factory claimed performance with even the most ridiculously careful driving.

I would be happy if I could set a higher value for switching to gas or if I had an EV ONLY switch that I could use to take the top 20% or so of energy from the hybrid battery. But it appears that EV mode is almost unused. A one mode engine can switch off the engine at stops and coasting. My two mode engine does not seem to do hardly any more. And I get 15 MPG instead of 22 MPG with careful city driving.

 

With a nearly 3-Ton hybrid the power required to accelerate fast enough to keep traffic behind you off the horn exceeds the 33kW 46HP maximum that the battery will provide. Your truck is not an EV, it has limited EV capability.


To accelerate above 10 MPH and stay electric is very difficult and takes a long time. Typically to do it you will hold up traffic. To stay electric above 20 mph is also difficult.


Now on to drive cycles and temperatures. Less than 20 mile drive cycles will not get you all the benefits of the hybrid system. Definitely 10 and less you may as well not have the hybrid.


Unless, you park it and live where it never gets near freezing of above 90F.


When parked in 20F for more than 18 hours, it can take 45 minutes of operation with the cabin heat on in order to warm up the HV battery to maximum power allowed. Down near and below freezing the battery power is limited. This means the engine will come on sooner than a 70F battery. Above 110F battery and you are limited again.


So what are the outside temperatures for you? What happens when you drive a 100 mile plus run?

 

I live in a very mild temperature area with 60 to 75F being my normal outside temperature while driving. It never gets near freezing or above 90F.

On a 100 mile run, I am going at highway speeds. My engine shifts to 4 cylinder operation and the milage is good for a pickup. 20 to 22 MPG. The engine turns off at a stop and starts again just fine. Hardly any EV mode.

Does the engine start with the hybrid battery? I thought it started with the conventional battery. If I stop the car and turn off the engine, the battery readout is 15volts. Then I listen to the radio for a few minutes and the readout drops to 13volts. Now, I get a warning that says "Start the engine, battery low." and the radio shuts off. 12.6 volts is a fully charged battery. It should be about 11.5 volts before there is a danger of not starting unless the battery is defective and can not deliver current.

But I have the impression that you are saying that the hybrid battery starts the car. I think you said that it needs to reserve 10 HP in order to restart the engine.

My present hypothesis is that General Motors gamed the EPA system and falsely claimed that the truck would get over 20MPG in the standard mileage test when it, in fact, only will get 15 MPG. I have read the details of the test procedure and my driving is more conservative than the test requirements. I suppose that I should complain to the EPA. Given that Volkswagen did a massive fraud on its diesel engines, it would not be too amazing to find that GM did something similar.

 

The high voltage battery is the heart. It starts the engine not the 12V. There is no starter and no alternator. Instead it uses the hybrid transmission to start the engine. Yes it will reserve up to 10 HP of HV electrical power for an immediate engine start if needed.


So the High Voltage to 12V DC-to-DC converter is using about 1 HP. The numerous gadgets use in my opinion way too much 12V power. So Auto-Stop for just sitting is your best bet.


The vehicle gets the rated fuel economy on the Federal Test or it would be in trouble just like VW. In fact the VW scandal has everybody back under the microscope.


So for the city FE. I'm not sure what to suggest. Your experience is an anomaly. If it can get 20 plus on the highway, it can in the city. However not on short hops.

 

Actually the battery readout says 15 volts when I turn the key off. After a few minutes of radio with the engine off, it reads 13 volts. Is the 300 to 12 volt converter running?

The 300 volt battery provides heavy discharge when the truck does fast acceleration. Maybe there are some dead cells. A battery could have specified voltage with no load, but go dead when drawing power. 10.5/12 = .875 for a dead 12 volt battery. 13/15 = .867 Does this indicate that the hybrid battery is almost dead? The computer turns off the radio and says to start the engine immediately. This is a repeatable condition that I can show to a mechanic. Would they find it meaningful?

Previously on the highway, the discharge went to 100% while driving 60 mph on flat road. It continued for several minutes and then stopped. I reported this to the dealer, but it was not repeatable and led to no diagnosis.

In order to get 20 MPG city, it must be able to get 20 MPG over some distance. I can drive it for a long warmup and then start the measure. It will be totally warm. And it still will not get 20 MPG in town. The dealer just says that everything checks out and will not respond to the fact that it will not get close to EPA mileage.

I am very thankful that you are trying to help me. You are the only one.

 

Are you turning the truck off then key back to Run in order to listen to the radio?


To see on the display what the digital value of the 12V system is, you must be in key to Run not Accessory.


If so the vehicle is using way more 12V power and since the 12V will not charge without the propulsion system able to go, the 12V will drop fast.


What is discharging at 100%. The "EFF" gage? That thing is not an accurate indicator of much other than total system intended acceleration or deceleration.

 

Yes, by 100% discharge, I mean that the dash gauge goes to the maximum movement extent of showing discharge. This discharge is adding boost to the accelerating engine. In contrast, when running in EV mode, the gauge barely shows any movement in the discharge direction.

My Ford Escape Hybrid uses hybrid boost to allow the Atkinson Cycle engine to have more acceleration while keeping fuel economy. I suppose that is what the Silverado also does.

You are correct that I was listening to the radio with the key in the Run position. So I take it that I should listen in the Accessory position instead. Thanks for setting me straight on that.

 

That top left Economy or Efficiency gage is a sort of indicator on total power. By trying to keep it in the solid green near centered area you are running the most efficient. Hard over one way and you are using the engine hard not battery. Hard over the other way and you are making HOT brake pads not Re-Generative braking. So it is an indicator of total system accelerations not battery use. Try to not let it get too far out of the solid green


So inside the + - 25% from center is most efficient. Maybe the first dash mark on left or right . Also I hope you are not shifting out of Drive for stops.