Oil temperature is one of the most overlooked variables in a performance build. Most builders focus on power and cooling water temperature, but sustained high oil temps are quietly destroying bearings, reducing viscosity, and shortening engine life — especially on track, in drift, or under any kind of sustained high-load use.
This guide covers how to choose the right oil cooler size for your build, how to plumb it correctly, and the common mistakes that make a cooler ineffective.
Why Oil Temperature Matters
Engine oil has an ideal operating temperature range of 80–110°C. Within this range, viscosity is correct, the oil film is strong, and the oil is doing its job properly.
Above 120°C, viscosity drops and film strength weakens — the oil can no longer maintain a consistent protective layer between moving parts. Sustained temperatures above 130°C accelerate bearing wear significantly. Above 150°C, most mineral oils begin to break down chemically.
- Symptoms of overheating oil: rising oil temp gauge, increased oil consumption, metallic particles in oil, premature bearing wear
- Turbocharged engines: the turbo bearing is oil-cooled — high oil temps directly reduce turbo life
- Track and drift use: sustained high RPM and load means sustained high temps — road car oil cooling is not designed for this
Do You Actually Need an Oil Cooler?
Not every car needs one — but most performance builds do. Use this as a guide:
- Road car used occasionally on track: yes — even a few laps will push oil temps beyond the road car design limit
- Dedicated track, time attack, or hillclimb car: definitely yes
- Drift car: yes — sustained high RPM, aggressive driving, and often a turbocharged engine all combine to push oil temps hard
- Turbocharged engine (any use): strongly recommended — the turbo bearing depends on oil cooling
- Naturally aspirated road car, light use: probably not needed unless you're seeing high temps on a gauge
If you have an oil temperature gauge and you're seeing sustained readings above 110°C on track, a cooler is the correct fix.
How Oil Coolers Are Sized — Rows and Core Size
Oil coolers are rated by row count — the depth of the core. More rows = more surface area = more cooling capacity. Core width and height also matter, but row count is the primary sizing variable for most builds.
| Row Count | Cooling Capacity | Typical Application |
|---|---|---|
| 10 row | Light | Mild road use, light track days |
| 13 row | Medium | Regular track use, NA engines up to ~250bhp |
| 16 row | Medium-high | Frequent track use, mild forced induction |
| 19 row | High | Dedicated track car, turbo engines, time attack |
| 25 row | Very high | High-power forced induction, drift, competition |
| 30 row | Maximum | Endurance, extreme power, hot climates |
Rule of thumb: when in doubt, go one size up. An oversized cooler with a thermostat is always better than an undersized one without.
Maxflo Motorsport stocks oil coolers from 10 row to 30 row in AN10 — covering everything from occasional track use to full competition builds.
Thermostat — Do You Need One?
An oil cooler thermostat (also called a thermostatic sandwich plate or oil stat) allows oil to bypass the cooler until it reaches operating temperature, then opens to route oil through the cooler.
Without a thermostat: oil always flows through the cooler. In cold weather or on a cold engine, this means the oil takes much longer to reach operating temperature — causing increased wear during warmup and, over time, condensation and sludge buildup inside the engine.
With a thermostat: the engine warms up normally, the cooler only activates when needed, and oil temperature stays in the ideal range regardless of ambient conditions.
- Recommended for: road-legal cars, cold climates, cars used year-round, any car where warmup time matters
- Less critical for: dedicated track cars used only in warm conditions with a full warmup procedure before hard use
For most builds, a thermostatic sandwich plate is the cleanest solution — it combines the cooler connection and thermostat function in a single unit that fits between the engine block and oil filter.
The Maxflo Motorsport oil filter sandwich plate — fits between the engine block and oil filter, providing AN10 ports for cooler feed and return lines with no permanent engine modification.
Sandwich Plate vs Remote Filter Relocation
There are two main ways to connect an oil cooler to the engine:
Sandwich Plate
- Fits between the engine block and the existing oil filter
- No permanent modification to the engine
- Easiest install — typically 1–2 hours
- Correct for most builds
- Available with or without integrated thermostat
Remote Filter Relocation
- Moves the oil filter to a remote location (firewall, inner wing) via AN lines
- Allows a larger filter and easier access for oil changes
- Better for tight engine bays where a sandwich plate and cooler lines are difficult to route
- More complex install — requires blocking the original filter port and running longer lines
For most track and drift builds, a sandwich plate is the correct starting point. Remote relocation is worth considering if your engine bay is very tight or you're building a high-spec competition car.
Oil filter bypass adapter — used in remote filter relocation setups to block the original filter port and route oil via AN lines to a remote filter and cooler.
Plumbing an Oil Cooler — AN Sizing and Hose Choice
Oil cooler lines run hot, under pressure, and in close proximity to exhaust components. The correct specification is non-negotiable:
- Hose size: -10AN for most builds — matches the AN10 ports on our sandwich plates and coolers. Use -8AN only on smaller engines with lower oil flow requirements.
- Hose type: PTFE-lined stainless braided — handles oil temperature and pressure, chemically compatible, does not degrade over time. Do not use rubber-lined hose for oil cooler lines.
- Fittings: use 90° or 45° swivel hose ends at the sandwich plate and cooler to keep routing clean without tight hose bends
- Routing: keep lines away from exhaust manifolds and turbo downpipes — use heat sleeve where proximity is unavoidable
For full hose and fitting guidance, see:
AN8 90° PTFE swivel hose end — ideal for oil cooler line connections at the sandwich plate where a straight fitting would foul surrounding components.
Cooler Placement and Airflow
An oil cooler with no airflow is just a heat soak — it will make oil temperature worse, not better. Placement is as important as size.
- Front-mount (behind bumper/grille): best airflow, most common — position in front of or beside the radiator where it gets a direct ram air feed
- Side-mount (inner wing or splitter): useful for tight engine bays or where front space is taken by intercooler — needs ducting to work effectively
- Avoid: mounting inside the engine bay with no direct airflow path — the cooler will absorb heat from the engine bay rather than dissipate it
Practical tip: before cutting brackets or running permanent lines, tape a piece of cardboard over the cooler location and drive at speed — if you feel significant airflow behind it, the placement will work. If not, reposition before committing.
The Maxflo Motorsport dual pass oil cooler — the dual pass design routes oil across the full core width twice, maximising heat transfer for a given core size.
Common Sizing Mistakes
- Going too small to save money: a 10-row cooler on a 400bhp turbo car will do almost nothing — size correctly from the start
- No thermostat on a road car: overcooling causes condensation inside the engine, leading to sludge and accelerated wear — always fit a thermostat on a road-legal car
- Undersized AN lines: -6AN lines to a -10AN cooler will restrict flow and reduce cooling effectiveness — match line size to cooler port size
- Poor placement with no airflow: the most common mistake — a cooler in a dead air zone does nothing
- Rubber hose on oil lines: rubber degrades at sustained oil temperatures — always use PTFE stainless braided
Ready to Build?
Match your row count to your usage, add a thermostat if the car sees road use, plumb with -10AN PTFE stainless braided hose, and mount where it gets airflow. That's the complete formula for a correctly specified oil cooling system.
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