Quick Summary:
- Read SIPP left to right for size, body type, transmission, fuel.
- Use the first letter to match passenger numbers and luggage space.
- Confirm manual or automatic using the third letter before booking.
- Check the fourth letter for fuel type and air conditioning inclusion.
SIPP codes are a short, standardised way to describe a car hire class. Instead of relying on model photos or vague labels like “compact” or “standard”, the four letters tell you the broad size, the body style and doors, the transmission and drive, plus fuel type and whether air conditioning is included. This is especially useful when you are comparing options across airports and providers in the United Estates, where the vehicle you receive is typically “or similar”.
You will often see codes like CDMR or IFAR in search results. If you can decode them, you can choose a class that actually fits your passengers, luggage and driving plans, rather than guessing and hoping.
If you want to compare classes across different providers and locations, start from a single hub such as car hire United States, then use the SIPP code on each result to make an apples-to-apples comparison.
What a SIPP code looks like
A typical SIPP code has four letters. Each position has a meaning:
1st letter, vehicle category (rough size and segment).
2nd letter, vehicle type (body style, and sometimes door count).
3rd letter, transmission and drive (manual or automatic, 2WD or 4WD).
4th letter, fuel and air conditioning (petrol or diesel, with or without AC).
Not every market uses every possible letter in exactly the same way, but the structure is consistent enough that you can make far better choices than by category name alone.
Step 1, decode the first letter: size and segment
The first letter is your starting point because it drives cabin space and boot capacity. Common category letters you may see include:
M Mini, best for one or two people with light bags.
E Economy, small hatchbacks, efficient and easy to park.
C Compact, more shoulder room and usually a bigger boot.
I Intermediate, a step up in passenger comfort, often suitable for longer drives.
S Standard, more luggage capacity and rear-seat space.
F Fullsize, roomy for adults and larger cases.
P Premium, higher trim, often larger sedans or upscale models.
L Luxury, top-tier comfort and features.
X Special, non-standard categories, which vary by provider.
To match this to real needs, think in terms of people plus luggage. If you have four adults and two large suitcases, “compact” can be tight even if it technically seats five. Moving up to intermediate or standard often changes the trip from cramped to comfortable.
When you are comparing vehicle groups on a broader page such as car rental United States, use that first letter as your primary filter, then refine with the remaining letters to ensure the configuration matches your trip.
Step 2, decode the second letter: body style and doors
The second letter tells you the vehicle type. This is where you confirm whether you are getting a hatchback, saloon, estate, people carrier, or SUV. Common letters include:
D 4-door saloon (or similar).
B 2-door model (less common in mainstream airport fleets).
C 2 or 4-door, depending on fleet, often compact hatchback classes.
W Estate (wagon), useful for bulky luggage.
V Passenger van or people carrier.
F SUV, typically higher ride height and more cargo flexibility.
P Pickup, often classified under special or regional groups.
This letter matters because a “compact” can be either a small saloon with a separate boot or a hatchback with a wider opening. If you have a pram, golf clubs, or oddly shaped luggage, a hatch or estate style is usually easier.
For road trips, national parks, or winter destinations, you may find more SUV-coded groups, and you can compare them by looking at pages such as SUV rental United States, then confirming the exact SIPP on each listing.
Step 3, decode the third letter: transmission and drive
The third letter is often the most critical detail for travellers, because it confirms manual versus automatic. In the United Estates, automatic cars are common, but it still pays to check because some smaller or special classes can be manual.
Common third-letter meanings include:
M Manual transmission, typically 2WD.
A Automatic transmission, typically 2WD.
N Manual, 4WD (less common).
B Automatic, 4WD.
If you are only comfortable driving automatic, treat this letter as non-negotiable. Likewise, if your itinerary includes mountain roads, snow conditions, or unpaved sections, you may prefer a 4WD code. That said, 4WD does not automatically mean better in all situations, it can cost more and use more fuel.
Step 4, decode the fourth letter: fuel type and air conditioning
The fourth letter combines fuel type and whether air conditioning is included. Common examples are:
R Unspecified fuel with air conditioning, often interpreted as petrol with AC.
N Unspecified fuel with no air conditioning.
D Diesel with air conditioning.
Q Diesel with no air conditioning.
H Hybrid with air conditioning (when offered in a fleet).
Air conditioning is the detail many people forget to check, and it can matter a lot depending on season and region. If you are travelling with children, driving long distances, or visiting warmer areas, prioritise an AC code.
How to choose the right SIPP for passengers and luggage
Use a simple checklist when you compare car hire classes:
1) Count adults, not just seats. “Seats 5” often means 4 adults plus a child seat realistically. If you have five adults, start at intermediate or standard and prioritise wider body types.
2) Count large cases, not bags. Two cabin bags can fit almost anywhere, two large suitcases can fill a compact boot quickly. Estates and SUVs can help, but the first-letter category still drives overall volume.
3) Decide on transmission before price. If you need automatic, filter to codes with “A” or “B” in the third position so you are not comparing unsuitable deals.
4) Consider the trip profile. City breaks suit economy or compact. Multi-state drives often feel better in intermediate, standard, or fullsize. Snowy routes may justify 4WD.
If you are comparing providers, it can help to scan several supplier pages and see how frequently a particular SIPP appears for your dates. For example, you might compare fleet styles across Budget car rental United States and National car rental United States, then use the SIPP code to confirm you are looking at the same class.
Common mistakes when using SIPP codes
Assuming the photo is the exact car. Most bookings are for a group, not a specific model. Trust the SIPP structure more than the image.
Ignoring the second letter. “Intermediate” can mean a saloon, an estate, or an SUV depending on the type letter. That changes luggage practicality.
Not checking AC. The fourth letter is easy to overlook, but it can make a big comfort difference.
FAQ
What does a SIPP code mean for car hire? A SIPP code is a four-letter shorthand that describes the car hire class: category, body type, transmission and drive, plus fuel and air conditioning.
Are SIPP codes the same across the United Estates? They are broadly consistent, but some letters can vary slightly by provider and fleet. The four-position structure stays the same, so you can still compare classes reliably.
How can I tell if a car is automatic from the SIPP code? Check the third letter. “A” typically means automatic 2WD, and “B” typically means automatic 4WD. “M” is usually manual.
Does the SIPP code guarantee the exact model I will receive? No. It indicates the class and key features, and you typically receive a vehicle that matches the code, or a similar model in the same group.
Which SIPP letters matter most for luggage? The first letter (category size) and the second letter (body type) matter most. An estate or SUV type can be easier for bulky items, even within the same size category.
