AEP supplies Gunson tools like gastester, colortune, eezibleed, clickadjust and carbalancer at competitive prices and with a dedication to customer support. AEP stocks all Gunson products imported to the US. If we can't get it no one can.

AEP was established by John Abbott in 1993 to assist home mechanics with unique and afforadable tools to ease maintenance and tuning challenges. John was introduced to Eezibleed during replacement of master cylinder in a 1985 Audi 5000s. The British Haynes manual suggested using an Eezibleed to replace the brake fluid. The rest is history.

Gastester Digital

Fine tune your muscle or classic car, or motorcycle with an affordable and accurate exhaust gas analyzer and take the guesswork out of tuning.

Gastester is not designed for on the road measurements. A better choice is the LM-1 air fuel ratio from Innovate Morotsports. I use an ELM 327 with Turbo Torque app for Android to read OBD II data and read and reset check engine light.

Gunson tools are legendary in the U.K. where they have been helping the do-it-yourselfer tune and maintain their vehicles for decades.Gunson Tools

Gastester Digital measures carbon monoxide the principal indicator of air fuel ratio and combustion efficiency. Use gastester to tune for performance or to pass a state mandated emissions test. The advantage is a digital readout that shows the level of carbon monoxide which can be translated into an air fuel ratio using the provided conversion table. So stop tuning by ear and start tuning your car, truck, fork lift, snowmobile, jet ski or motorcycle the professional way with an exhaust gas analyzer that's proven in 20 years of customer use.

Product support is only a phone call away. But please AEP customers only.


Colortune has been proven over time. Since the 1950's, before OBD and exhaust gas analyzers, Colortune has helped the DIYer tune for optimum performace. Colortune is a diagnostic spark plug with a glass top that lets you see the color of combustion. A blue flame means the mixture is rich; yellow flame means mixture is lean. There was a purpose to high school chemistry: a gas mixture burns with a specific color value based on the oxygen content; a blue flame will burn hotter indicating complete combustion. A yellow flame indicates incomplete combustion and is considered "dirty" because it leaves a layer of carbon on whatever it is heating.

Colortune Instructions

Colortune Chart

Product Info Sheet


Another Gunson classic, Eezibleed is a one person brake bleeder used to change-out brake fluid. I leanred about Eezibleed in the late 80's when a changed the master cyclinder in my 1985 Audi 5000s and wanted a painless and effective method to refill the system. I found the answer in the Haynes manual, Eezibleed. Finding Eezibleed before the Internet was a challenge but quest launched Auto Expert Products and the rest is history.

Eezibleed Instructions




Eezibleed $39.95

Buy Eezibleed

Multi-purpose Cap $23.95

Pressure bleeding requires a tight fitting cap. European cars with ATE reservoirs use screw on cap and a 45mm cap is included in the Eezibleed kit. Japanese and American cars use twist on caps. A reservoir with a twist on cap can not be pressurized so you have to use the multipurpose cap or the old school method with the help of an assistant.

Multi-purpose cap instructions

Buy Multi-Purpose Cap

Product Manuals

Gastester Instructions

Colortune Instructions

Clickadjust Instructions

Carbalancer Instructions

Eezibleed Instructions




Carbalancer $29.95


Buy Carbalancer

clickadjust $59.95


Buy clickadjust

Gunson Products

Gasteter $229.95


Buy Gastester

Colortune Kits $69.95, 10mm, 12mm and 14mm


Colortune Kits
Buy Colortune

Colortune Kit

Order the right size

Look up your vehicle in the NGK product guide to makes sure you need a 14mm colortune. Most cars use 14mm plugs. If unsure ask me.

NGK Plugs

Use the first letter of the product code to determine the adapter. Remember colortune comes with 14mm threads.

  • A - 18mm
  • B - 14mm
  • C - 10mm
  • D - 12mm
  • J - 12mm

How to decode spark plug codes guide (NGK)

Colortune adapters: 10mm, 12mm, 14mm long, 18mm

Available for 14mm Colortune only.

These kits converts the thread on Colortune to fit most popular sizes of spark plugs fitted to most modern and classic cars, motorcycles, garden machinery and boats. Contents 1 x Thread Adaptor (10mm,12mm,14mm or18mm), 1 x Gas Seal Washer 1 x Hex Key (with 18mm adaptor only.

Colortune Adapter

12mm adapter

14mm long reach colortune adapter

14mm adapter long reach

14mm long colortune adapter

14mm adapter taper slim

10mm adapter

18mm adapter