# Four vs Automobile Engineering Book

The clearest difference is in-app purchases: Four at none against Automobile Engineering Book's 5. Four also leads on ratings volume (96 vs 9) and iOS requirement (8.0 vs 14.0). Automobile Engineering Book's advantage is update cadence (every 5 weeks vs every 7 months) and review sentiment (100% vs 92%). On price, rating, ads and device support there is nothing between them.

Both are free to download. Automobile Engineering Book sells 4 in-app purchases, starting at $2.99 per 3 months. Four asks for nothing beyond the download.

On the App Store both sit at effectively the same score — 4.7 for Four against 4.6 for Automobile Engineering Book. That said, the two scores are not equally well evidenced: Four has 96 ratings behind it against 9, so its average is the more settled of the two. Written reviews are what separate them: 92% of Four's written reviews are positive against 100% of Automobile Engineering Book's.

Four ships an update every 7 months, Automobile Engineering Book every 5 weeks. Both last shipped on October 24, 2026.

## The numbers

| Metric | Four | Automobile Engineering Book |
| --- | --- | --- |
| Price | Free | Free |
| Rating | **[4.7 (96 ratings)](https://appshunter.io/ios/app/four-stroke-otto-engine-3d/id1376010957/reviews)** | [4.6 (9 ratings)](https://appshunter.io/ios/app/automobile-engineering-book/id1583758958/reviews) |
| Number of ratings | **96** | 9 |
| Positive reviews | 92.0% of reviews | **100.0% of reviews** |
| In-app purchases | **No** | Yes |
| Ads | No | No |
| Update frequency | Every 7 months | **Every 5 weeks** |
| Monetization | **Free** | Free with in-app purchases |
| Size | 183 MB | 136 MB |
| Requires iOS | **8.0** | 14.0 |
| Devices | iPhone, iPad, iPod | iPhone, iPad, iPod |
| Age rating | 4+ | 4+ |
| Developer | [MOZAIK Education Ltd.](https://appshunter.io/developer/1064850236) | [Oleksandr Pereshein](https://appshunter.io/developer/1041461209) |

## What reviewers say

### Four

[App page](https://appshunter.io/ios/app/four-stroke-otto-engine-3d/id1376010957)

Explore the inner workings of a four-stroke Otto engine through interactive 3D animations. This app offers an engaging way to learn about automotive technology with features like rotation, zooming, and predefined views. It's designed for students but enjoyable for all ages, with multilingual support and VR capabilities.

**Highlights:** Interactive 3D engine model, Rotate, zoom, and pan views, Predefined navigation angles, Multilingual support, VR mode compatibility, Built-in animations and narrations

**Features:** macOS Compatibility

**In-app purchases:** none


### Automobile Engineering Book

[App page](https://appshunter.io/ios/app/automobile-engineering-book/id1583758958)

This app provides a comprehensive yet accessible guide to automobile engineering. It covers basic vehicle structure, common malfunctions, and maintenance rules in a clear, engaging format with ample illustrations. Ideal for novice drivers and anyone seeking to understand their car better.

**Highlights:** Basic vehicle structure information, Common malfunctions and solutions, Operation and maintenance rules, Simple language explanations of car systems, Extensive illustrative material

**Features:** macOS Compatibility, Vision Pro support

**In-app purchases (4)**

| Purchase | Price | Billing |
| --- | --- | --- |
| Full version | $2.99 | per 3 months |
| Full version for three months | $2.99 | one-time |
| Full version for one year | $4.99 | one-time |
| Full version forever | $6.99 | one-time |


## Frequently asked questions

### Is Four free?

Four is free to download, with no in-app purchases.

### Is Automobile Engineering Book free?

Automobile Engineering Book is free to download, with in-app purchases available.

### Which has better reviews, Four or Automobile Engineering Book?

Four is rated higher. Four averages 4.7 out of 5 from 96 ratings, while Automobile Engineering Book averages 4.6 from 9 ratings.

### Do Four or Automobile Engineering Book have ads?

Neither Four nor Automobile Engineering Book shows ads.

### Which is updated more often, Four or Automobile Engineering Book?

Four ships an update every 7 months, and Automobile Engineering Book every 5 weeks. Most recently, Four was updated on October 24, 2026 and Automobile Engineering Book on October 24, 2026.

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*Compared by [AppsHunter](https://appshunter.io/) from daily US App Store data. Review summaries are generated from verbatim App Store reviews.*