Spark plug replacement - Fuel consumption?

[noogieman]

Recently I took my car to a shop for an annual oil change and the dreaded 16x spark plug replacement.
I bought NGK PFR5R11 Laser Platinum plugs suitable for M113 engines.

How much does a fresh plug replacement affect fuel consumption?
Does fuel consumption improve very little or very much with new plugs fitted?

Last summer I had my air filters and filter box cleaned with compressed air, they weren't filthy at all.
I also had all vacuum hoses replaced and gaskets for valve covers.

All these things fixed must improve fuel consumption, does it????

Thanx

 

[190]

Unless the plugs were in a terrible state Id be surprised if you notice much if any difference. New plugs helped when ignition systems were marginal but these days they have spark energy to spare.

 

[AltonAnt]

As above and to add especially with two plugs per cylinder.
TBH though, fuel economy shouldn’t be the top of your concerns with an M113.

 

[noogieman]

MB claims spark plug replacement must be done every 4 year if I remember correct?

I have passed due date with several years as I don't drive my car very often, it's more of a weekend cruiser on sunny days!
B4 spark plug replacement my car ran fine with the old plugs, it started everytime, there were no idle issues or anything else.

I mean fresh ignition parts must do something for mpg?
I don't worry much about fuel consumption as it's a V8.

I just wonder if fresh plugs and fresh engine oil will do anything to improve fuel economy?
I think it does a little when fitting new ignition parts but how much?
That's the million dollar Q?

 

[flowrider]

I'm going by mileage on my spark plugs rather that time. I did mine 3 years ago as they were still the originals.

 

[noogieman]

I'm going by mileage on my spark plugs rather that time. I did mine 3 years ago as they were still the originals.

Every 4 year replacement or replacing plugs at a certain mileage?
Can't remember what the mileage intervals are but I'm quite sure I didn't cover those?

I think my plugs were replaced back in 2008 or 2009, that was a long time ago.

 

[R129mine]

I believe it is every 30k

 

[noogieman]

I believe it is every 30k

Thanx.

30k comes to 48000km
I'm sure I didn't cover the mileage on my plugs.

 

[Deleted member 149005]

I thought the time based interval for plugs was more to do with ensuring they don’t seize in the thread???

Even if you don’t replace them it is worth taking them out and reinstalling.

 

[markjay]

I thought the time based interval for plugs was more to do with ensuring they don’t seize in the thread???

Even if you don’t replace them it is worth taking them out and reinstalling.

As above.

Modern spark plugs can last for very high mileage, plug manufacturers quote 40,000 Mike's 80,000 miles, and sometimes even higher.

And, while Iridium spark plugs won't gain you any performance advantage over Platinum, they are among the longest lasting spark plugs on the market.

The main reason that manufacturers specify change intervals is to avoid seizing.

As for resisting the plugs... it's possible, but the torque setting will suffer.

 

[flowrider]

R230 SL500 spark plug changes is 4 years or 60k miles. Mine were done 3 years ago but only 2k miles ago so there is no way I will change them next year. The plugs were original when I had them changed, the car was 12 years old and had covered 52k miles.

 

[noogieman]

Enthusiasts cars won't be driven the way MB had their intentions per their recommendations.
These cars are driven on sunny days.
We can't follow their recommendations on gearbox oil changes or spark plug interval replacement.
It will be very costly if we follow MB service intervals and drive very little per year.

When it comes to annual A - B service, I do this every 2 years at a specialist.
For engine oil and filter changes, I do this every year.

 

[flowrider]

My SL is serviced by an MB Indy and I follow his recommendations given my car's usage so that means oil change every 2 years, brake fluid change every 2 years and ABC fluid change every 4 years.

 

[Will]

Unless your old plugs are causing a misfire they can’t have any significant effect on your fuel consumption or anything else.

The servicing schedule is more to do with preventative maintenance, to prevent your plugs from being worn out or stuck in the cylinder head.

Changing the oil before the specified time is pointless, M113s are exceptionally durable engines and changing the oil in advance of schedule is costing you money that could be better spent elsewhere

The mixture is electronically controlled in closed loop, the various sensors involved in mixture control and efficient combustion (eg lambda/o2 sensors, MAF sensor for example) probably have more potential for improvement in economy if they’ve deteriorated or out of spec. Changing the oil with minimal usage isn’t going to help you there.

A little confused at the post, as said you doing buy a V8 AMG for fuel economy reasons and then you say you don’t drive it very often But at least fuel is cheap at the moment

 

[noogieman]

Unless your old plugs are causing a misfire they can’t have any significant effect on your fuel consumption or anything else.

The servicing schedule is more to do with preventative maintenance, to prevent your plugs from being worn out or stuck in the cylinder head.

Changing the oil before the specified time is pointless, M113s are exceptionally durable engines and changing the oil in advance of schedule is costing you money that could be better spent elsewhere

The mixture is electronically controlled in closed loop, the various sensors involved in mixture control and efficient combustion (eg lambda/o2 sensors, MAF sensor for example) probably have more potential for improvement in economy if they’ve deteriorated or out of spec. Changing the oil with minimal usage isn’t going to help you there.

A little confused at the post, as said you doing buy a V8 AMG for fuel economy reasons and then you say you don’t drive it very often But at least fuel is cheap at the moment

I only drive her when I feel like it on sunny days.
You're correct fuel prices dropped recently, that's a good thing meaning, driving should be cheap this year compared to 2019.

How do I notice if I had a misfire?
I have never thought about this?
Would it cause a lumpy idle?
I have no such things.

Reason I asked about the new plugs if they improve fuel economy?
I noticed while driving normal within legal speed limits, my fuel gauge needle drops a little fast after I had the air duct housing with gaskets replaced and my air filters cleaned with compressed air last summer.
Feels like my car consumes more fuel when the needle drops a little faster?
I don't know maybe I'm just hypochondriac about this?
I like to drive like the devul himself and I do this sometimes, it's natural that car consumes more fuel this way, but in normal driving it should consume less petrol.

Oil changes are done after the asysst system counts down for service every two years.
In between I do an annual oil change but don't reset the asysst

 

[Muckypaps]

Unless your old plugs are causing a misfire they can’t have any significant effect on your fuel consumption or anything else.

At last a sensible answer.

 

[Will]

The garage who service your car, if they have access to the proper Mercedes workshop system, can look into the engine live data, sensor values, smooth running, mixture, etc.

People often seem to needlessly replace some parts on cars to make themselves feel good (I’m not referring to your plugs here) but in truth there’s often plenty of other stuff that’s overlooked. Eg plugs can cause misfires, but so can faulty coil packs or leads. But people seem to replace their plugs every four years and never consider the bits that aren’t included on the service schedule. In my opinion that’s quite relevant as these cars get older, and more common issues come to light. Some parts are known to give problems, other stuff rarely does. That’s where sharing experience and advice on forums is so useful.

I wouldn’t rely too much on the needle readings for your fuel consumption. You can work out more accurately from brim to brim fills and calculating the distance travelled - but unless it’s causing you real concern, why worry?

And others often seem to quote/know their fuel consumption on performance cars, but to be honest with you the majority of the time I couldn’t really tell you, unless I made a point of looking at the reading on the instrument cluster or a long journey etc. Why worry? Most of the time, serious misfires or incorrect combustion will flag a code or EML - other than that let your garage do the checking at service time.

I think you’re worrying too much and looking to notice stuff as you know that’s been done. It’s a bit like how a clean car always seem to drive better..!

If it ain’t broke though, don’t worry. Stick with your garage’s recommendations and enjoy

 

[BlackC55]

Air mass and Lambda values play a big part in fuel economy. When lambda sensors get old, they get lazy.

Oh and the advice from Will is spot on. If it aint broke....

 

[noogieman]

The garage who service your car, if they have access to the proper Mercedes workshop system, can look into the engine live data, sensor values, smooth running, mixture, etc.

People often seem to needlessly replace some parts on cars to make themselves feel good (I’m not referring to your plugs here) but in truth there’s often plenty of other stuff that’s overlooked. Eg plugs can cause misfires, but so can faulty coil packs or leads. But people seem to replace their plugs every four years and never consider the bits that aren’t included on the service schedule. In my opinion that’s quite relevant as these cars get older, and more common issues come to light. Some parts are known to give problems, other stuff rarely does. That’s where sharing experience and advice on forums is so useful.

I wouldn’t rely too much on the needle readings for your fuel consumption. You can work out more accurately from brim to brim fills and calculating the distance travelled - but unless it’s causing you real concern, why worry?

And others often seem to quote/know their fuel consumption on performance cars, but to be honest with you the majority of the time I couldn’t really tell you, unless I made a point of looking at the reading on the instrument cluster or a long journey etc. Why worry? Most of the time, serious misfires or incorrect combustion will flag a code or EML - other than that let your garage do the checking at service time.

I think you’re worrying too much and looking to notice stuff as you know that’s been done. It’s a bit like how a clean car always seem to drive better..!

If it ain’t broke though, don’t worry. Stick with your garage’s recommendations and enjoy

My car runs like a champion, it's been well maintained over the years!
When I hit the throttle, she's very quick.
Only things I haven't touched are coil packs and plug wires.

I have attached a photo of my fuel gauge where I have put a red line.
Top mark 1/1 and the mark below the 1/1 is that 15 litres gap between the two markings?
I drove like 100 kilometers within speed limits and fuel gauge almost touch the mark below 1/1.
That's what worried me if my old plugs were too worn and fitting new plugs would improve combustion and fuel economy?
Sorry I can't make a better description.

I replaced my lambda sensors maybe 14 years ago?
Bosch claims 100,000 miles guarantee on these oxygen sensors, but they may fail before 100,000 miles!
Air mass sensor was also replaced some years ago.

 

[noogieman]

Air mass and Lambda values play a big part in fuel economy. When lambda sensors get old, they get lazy.

Oh and the advice from Will is spot on. If it aint broke....

My car pass MOT test every year with flying colors.
Readings from exhaust fumes are within tolerances