Recently bought a 2018 Ford S Max 1.5 Petrol with 52k on the clock. Looks and drives well until you look at the mpg. It’s doing 17 mpg in the city and 26mpg on the motorway. Took it back to the dealer and he said he can’t find anything wrong mechanically just drive it for another month and calculate mpg manually instead of using trip computer. This seems rubbish as I know we’re spending more on fuel! Read on the internet possible faults might be misfiring due to cracks in the engine cylinders or due to coolant loss. This sounds serious or expensive. Anyone experienced similar issues? 

The S-Max is a heavy car with all the aerodynamics of a brick.  Presumably loaded up with family members and a bootfull most of the time as well?  Wrong engine for this type of car unfortunately, too small and wrong fuel type.

Having said that, your MPG is still low.  I'd be expecting nearer 30mpg combined.  

This will be the 4 cylinder 1.5 EcoBoost, and it is known for the cylinder liners slipping.  Theoretically it's possible to repair, but in the UK it's more realistic to replace the whole engine when this fault occurs.  Should be easy enough to test as the coolant level will be dropping in the reservoir.  Personally, if you've got the option to return the car, that's what I'd do, and buy another one with a bigger engine, it'll be better on fuel as not working so hard.

S-Max 2.0 diesel, 55MPG

https://www.cargurus.co.uk/Cars/inventorylisting/vdp.action?listingId=156281828&entitySelectingHelper.selectedEntity=d3097&zip=NE12 6RU&pid=directVDPSimilarListing#listing=156281828

2 hours ago, TomsFocus said:

The S-Max is a heavy car with all the aerodynamics of a brick.  Presumably loaded up with family members and a bootfull most of the time as well?  Wrong engine for this type of car unfortunately, too small and wrong fuel type.

Having said that, your MPG is still low.  I'd be expecting nearer 30mpg combined.  

This will be the 4 cylinder 1.5 EcoBoost, and it is known for the cylinder liners slipping.  Theoretically it's possible to repair, but in the UK it's more realistic to replace the whole engine when this fault occurs.  Should be easy enough to test as the coolant level will be dropping in the reservoir.  Personally, if you've got the option to return the car, that's what I'd do, and buy another one with a bigger engine, it'll be better on fuel as not working so hard.

Thanks for your comments. Car usually only has 1 lightweight wife and two skinny kids in it most of the times as I’m on my bike! We only need 7 seats a couple of times a week. 
 

Does cylinder liners slipping cause the same issue as cracks in the engine cylinders (got minimal mechanical knowledge)? 
 

Can you return a car when it’s under warranty from a second hand car dealer? 
 

There is a recall on the front brake hose which the local Ford dealership are fixing so I have agreed to pay £114 for them to run a full diagnostic on the engine for the fuel efficiency issue. I then should be able to go back to dealer under the warranty.  Bit gutted I went for the petrol eco boost, based on short city journeys, instead of the diesel option. 

10 hours ago, S Maxxed Out said:

Thanks for your comments. Car usually only has 1 lightweight wife and two skinny kids in it most of the times as I’m on my bike! We only need 7 seats a couple of times a week. 
 

Does cylinder liners slipping cause the same issue as cracks in the engine cylinders (got minimal mechanical knowledge)? 
 

Can you return a car when it’s under warranty from a second hand car dealer? 
 

There is a recall on the front brake hose which the local Ford dealership are fixing so I have agreed to pay £114 for them to run a full diagnostic on the engine for the fuel efficiency issue. I then should be able to go back to dealer under the warranty.  Bit gutted I went for the petrol eco boost, based on short city journeys, instead of the diesel option. 

Without getting too technical, yes the same symptoms would appear from either a crack or a slip.  Basically just means that coolant can get into the cylinder, and exhaust from the cylinder can get into the coolant.  Requires a major engine strip to diagnose properly, and by that point it's cost hours of labour that would have been better spent on just replacing the whole engine.

Warranty is a separate thing, usually offered by a 3rd party if bought from an independent trader.  But if the car is not sold as advertised, or if it has a major fault, then you may be able to return it under consumer rights.  (I've had to return 3 cars myself over 10 years).

2 hours ago, TomsFocus said:

Without getting too technical, yes the same symptoms would appear from either a crack or a slip.  Basically just means that coolant can get into the cylinder, and exhaust from the cylinder can get into the coolant.  Requires a major engine strip to diagnose properly, and by that point it's cost hours of labour that would have been better spent on just replacing the whole engine.

Warranty is a separate thing, usually offered by a 3rd party if bought from an independent trader.  But if the car is not sold as advertised, or if it has a major fault, then you may be able to return it under consumer rights.  (I've had to return 3 cars myself over 10 years).

Thanks very much. I read a bit about warranties and consumer rights last night. It mentioned the tricky bit can be proving the fault was already there when we bought the car. However as it’s done around 17mpg since we got it, I think it is a pre existing fault. Just a shame I didn’t know about consumer rights otherwise I would have taken it back with 30 days and claimed a full refund. 

Based on your advice not sure paying Ford £114 for engine diagnostic will help then find the actual cause of the problem but I’m hoping it will provide me enough evidence to go back to the dealer or warranty company. Have 3 months warranty with dealer and 2 years with Handler protect. 
 

Thanks again, 

Andy 

 

15 hours ago, TomsFocus said:

The S-Max is a heavy car with all the aerodynamics of a brick.  Presumably loaded up with family members and a bootfull most of the time as well?  Wrong engine for this type of car unfortunately, too small and wrong fuel type.

Having said that, your MPG is still low.  I'd be expecting nearer 30mpg combined.  

This will be the 4 cylinder 1.5 EcoBoost, and it is known for the cylinder liners slipping.  Theoretically it's possible to repair, but in the UK it's more realistic to replace the whole engine when this fault occurs.  Should be easy enough to test as the coolant level will be dropping in the reservoir.  Personally, if you've got the option to return the car, that's what I'd do, and buy another one with a bigger engine, it'll be better on fuel as not working so hard.

Thanks for your comments. Car usually only has 1 lightweight wife and two skinny kids in it most of the times as I’m on my bike! We only need 7 seats a couple of times a week. 
 

Does cylinder liners slipping cause the same issue as cracks in the engine cylinders (got minimal mechanical knowledge)? 
 

Can you return a car when it’s under warranty from a second hand car dealer? 
 

There is a recall on the front brake hose which the local Ford dealership are fixing so I have agreed to pay £114 for them to run a full diagnostic on the engine for the fuel efficiency issue. I then should be able to go back to dealer under the warranty.  Bit gutted I went for the petrol eco boost, based on short city journeys, instead of the diesel option. 

So took the car back to Ford and they couldn’t find any issue other than the engine is running rich. 

Monitored fuel consumption over the last month and Fuelly app says we’re averaging 16 mpg. Trip display on dash says 20 mpg. 

Coolant level seems to have stayed the same in this time but Ford say we need to top up the antifreeze as it’s only showing -12 at the moment. 

Is it time to cut my losses and talk to car salesman about returning the car? I think as it’s been nearly two months so our consumer rights mean they have to repair or replace. Don’t trust them with this repair and they are unlikely have a suitable replacement as they are very small dealer. Not sure if I can get my money back on 2 year warranty either. 

18 minutes ago, S Maxxed Out said:

So took the car back to Ford and they couldn’t find any issue other than the engine is running rich. 

Monitored fuel consumption over the last month and Fuelly app says we’re averaging 16 mpg. Trip display on dash says 20 mpg. 

Coolant level seems to have stayed the same in this time but Ford say we need to top up the antifreeze as it’s only showing -12 at the moment. 

Is it time to cut my losses and talk to car salesman about returning the car? I think as it’s been nearly two months so our consumer rights mean they have to repair or replace. Don’t trust them with this repair and they are unlikely have a suitable replacement as they are very small dealer. Not sure if I can get my money back on 2 year warranty either. 

I think it'll be too late to return the car now unfortunately.  It'll also be difficult to claim a fault if Ford say there isn't one.  Did Ford not recommend or quote for any repairs?

1 hour ago, TomsFocus said:

I think it'll be too late to return the car now unfortunately.  It'll also be difficult to claim a fault if Ford say there isn't one.  Did Ford not recommend or quote for any repairs?

So took the car back to Ford and they couldn’t find any issue other than the engine is running rich. 

Monitored fuel consumption over the last month and Fuelly app says we’re averaging 16 mpg. Trip display on dash says 20 mpg. 

Coolant level seems to have stayed the same in this time but Ford say we need to top up the antifreeze as it’s only showing -12 at the moment. 

Is it time to cut my losses and talk to car salesman about returning the car? I think as it’s been nearly two months so our consumer rights mean they have to repair or replace. Don’t trust them with this repair and they are unlikely have a suitable replacement as they are very small dealer. Not sure if I can get my money back on 2 year warranty either. 

No I’m not sure how much of a diagnostic they did as they didn’t charge me the quoted £114. They did say they wanted to do a longer road test but as I was doing a long motorway journey, for me to test it out. It got to 28 mpg on the motorway after 4.5 hours of driving. 
 

I emailed the Ford dealership to ask if they tested the following things and am waiting a reply. These were all issues that may cause an S Max to run rich. 
 

• Faulty Oxygen (O2) Sensor: Often the most common cause, sending incorrect data to the ECU.
• Dirty or Faulty Mass Airflow (MAF) Sensor: Incorrectly measures air entering the engine.
• Leaking Fuel Injector: Leaks fuel directly into the chamber, causing a rich condition.
• Faulty Coolant Temperature Sensor:Fools the computer into thinking the engine is constantly cold, causing it to inject more fuel.
• Restricted Air Intake/Clogged Air Filter:Reduces air inflow, leading to an overly rich mix.
• Fuel Pressure Regulator Issues: Too much pressure can cause excessive fuel delivery.
• plus car salesman said they replaced the turbo charger so don’t know if that has caused issues.   
   
• Thanks for your quick response 

38 minutes ago, S Maxxed Out said:

I emailed the Ford dealership to ask if they tested the following things and am waiting a reply. These were all issues that may cause an S Max to run rich. 

Main dealerships don't really work like that I'm afraid.  They'll plug in the diagnostic and if no fault codes show up they won't just start testing individual items randomly.

Seems like it was a waste of time unfortunately.

(Also for future use, I don't think many garages will take kindly to being sent an AI list of things that might cause a fault.)

I have a Kuga MK2.5 with the same 4-cylinder 1.5 EcoBoost engine. I get 43 MPG for motorway-only driving and 28 MPG for a combination of motorway and urban driving.

In my opinion the 4-cylinder 1.5 EcoBoost engine is not particularly good on fuel.
 

Considering the fact that the S‑Max is heavier than the Kuga (by around 70 kg) and has a larger, less aerodynamic body, I expect the S‑Max to be less fuel-efficient, especially on long motorway journeys. The extra weight increases energy required for acceleration and stop-start traffic, while the larger frontal area and MPV shape increase aerodynamic drag at higher speeds, which hits motorway MPG the hardest.


The 1.5 EcoBoost is basically underpowered for the S-max and is therefore not the best choice. The 240 HP 2.0 EcoBoost is a much better choice.