Are these products a gimmick? Will adding things like STP injector cleaner or zMax oil treatment really improve function and longevity?

If yes, how often should they be used?

One bottle daily of your choice ............

Oh wait you're not talking about Makers Mark,

Most all of those are snake oil

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MUDD'S MOTORSPORT'S We do IFS lift installs ,
03 OVERLAND EDITION /Kilby-Skidrow-Mopar-4XGuard skids/ 2.5 inch TOTAL CONTROL JBA coilovers -JBA Arms/MOABS-31 FALKEN WILDPEAK AT3W / 4.10's etc, 04 Kilimanjaro Edition loaded, plus 05 KJ limited

I agree with Tom but I do use a bottle of Techron Fuel System Cleaner in the gas tank about once a year. The jeep seems to run real smooth when I use it but there are detergents in gas anyway. Probably better to take off the intake hose and clean the throttle body anyway. As far as oil goes, I just use a brand name synthetic and change it regularly. I don't see where you need to add anything to your oil.

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05 BLACK KJ - 42RLE & NP242
Skids, Hooks, Bent Rock Rail, Lifted, A/T's, etc.
NY and PA and Florida ONF Special Custom Organic Trail Rash

The oil additives are pretty much a waste of time and money - I don't know of any that actually deliver any observable improvements. On the other hand they generally don't do any harm either so may help your peace of mind If you are using a good quality modern engine oil though, it is very unlikely that any of the additives you can buy will improve it; if you are using poorer quality oil though (perhaps because of availability)they may help.

As for the fuel additives - they may well help, depending on the fuel you use and where you buy it. We've found here that supermarket fuels generally have fewer additives than forecourt, so if you use them exclusively the aftermarket additives will deliver an improvement. If you use brand name fuels or the uberdiesels/petrols though ( I can't recall the names applied to them by Shell, BP etc) it is unlikely that you will notice any improvement at all.

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Light Khaki 2.8CRD: TJM alloy bumper; Skid Row &Asfir skids;ext. breathers; SAMCO hoses; Grabber At3 235/70/16; Fumoto; Euro TC; Odyssey PC1500;GDE FTEcotune; OME lift; lightforce driving lights;ARB diff cover;nylon fan+Hayden2905;ss vortex exhaust; Airflow snorkel; Frontrunner roofrack; rock rails

I think a lot of the products out there are junk. STP might be ok in the oil, it seemed to help an older car I had years ago. it burned less oil with STP.

I do like seafoam and Lucas products in addition to power service for diesel fuels. I started putting pint of Lucas synthetic oil treatment with my oil change and I think my engine is quieter when idling after a cold start.

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2006 Liberty CRD Limited Deep Beryl Green Metallic Clear coat, Fumoto valve, MH ProVent (removed), GDE Eco tune,
OME 790/948 springs, OME struts, OME N132L shocks, Jeepin by Al A-arms, Hercules Terra Trac AT2 245/75R16
Weeks Stage 1 EGR delete, 5 volt steel glow plugs